
/*
 * Copyright (C) Igor Sysoev
 */


#include <ngx_config.h>
#include <ngx_core.h>
#include <ngx_http.h>

#define NGX_HTTP_SSI_MAX_PARAMS     16

#define NGX_HTTP_SSI_COMMAND_LEN    31
#define NGX_HTTP_SSI_PARAM_LEN      31
#define NGX_HTTP_SSI_PARAMS_N       4

#define NGX_HTTP_SSI_ERROR          1

#define NGX_HTTP_SSI_DATE_LEN       2048


#define NGX_HTTP_SSI_ADD_PREFIX     1


typedef struct {
    ngx_flag_t        enable;
    ngx_flag_t        silent_errors;
    ngx_flag_t        ignore_recycled_buffers;

    ngx_array_t      *types;     /* array of ngx_str_t */

    size_t            min_file_chunk;
    size_t            value_len;
} ngx_http_ssi_conf_t;


typedef struct {
    ngx_str_t          name;
    ngx_str_t          value;
} ngx_http_ssi_var_t;


typedef struct {
    ngx_buf_t         *buf;

    u_char            *pos;
    u_char            *copy_start;
    u_char            *copy_end;

    ngx_str_t          command;
    ngx_array_t        params;
    ngx_table_elt_t   *param;
    ngx_table_elt_t    params_array[NGX_HTTP_SSI_PARAMS_N];

    ngx_chain_t       *in;
    ngx_chain_t       *out;
    ngx_chain_t      **last_out;
    ngx_chain_t       *busy;
    ngx_chain_t       *free;

    ngx_uint_t         state;
    ngx_uint_t         saved_state;
    size_t             saved;
    size_t             looked;

    size_t             value_len;

    ngx_array_t        variables;

    ngx_uint_t         output;        /* unsigned  output:1; */

    ngx_str_t          timefmt;
    ngx_str_t          errmsg;
} ngx_http_ssi_ctx_t;


typedef ngx_int_t (*ngx_http_ssi_command_pt) (ngx_http_request_t *r,
    ngx_http_ssi_ctx_t *ctx, ngx_str_t **);


typedef struct {
    ngx_str_t                 name;
    ngx_uint_t                index;

    ngx_uint_t                mandatory;
} ngx_http_ssi_param_t;


typedef struct {
    ngx_str_t                 name;
    ngx_http_ssi_command_pt   handler;
    ngx_http_ssi_param_t     *params;

    unsigned                  conditional:1;
    unsigned                  flush:1;
} ngx_http_ssi_command_t;


typedef enum {
    ssi_start_state = 0,
    ssi_tag_state,
    ssi_comment0_state,
    ssi_comment1_state,
    ssi_sharp_state,
    ssi_precommand_state,
    ssi_command_state,
    ssi_preparam_state,
    ssi_param_state,
    ssi_preequal_state,
    ssi_prevalue_state,
    ssi_double_quoted_value_state,
    ssi_quoted_value_state,
    ssi_quoted_symbol_state,
    ssi_postparam_state,
    ssi_comment_end0_state,
    ssi_comment_end1_state,
    ssi_error_state,
    ssi_error_end0_state,
    ssi_error_end1_state
} ngx_http_ssi_state_e;


static ngx_int_t ngx_http_ssi_output(ngx_http_request_t *r,
    ngx_http_ssi_ctx_t *ctx);
static ngx_int_t ngx_http_ssi_parse(ngx_http_request_t *r,
    ngx_http_ssi_ctx_t *ctx);
static ngx_str_t *ngx_http_ssi_get_variable(ngx_http_request_t *r,
    ngx_str_t *name);
static ngx_int_t ngx_http_ssi_evaluate_string(ngx_http_request_t *r,
    ngx_http_ssi_ctx_t *ctx, ngx_str_t *text, ngx_uint_t flags);

static ngx_int_t ngx_http_ssi_include(ngx_http_request_t *r,
    ngx_http_ssi_ctx_t *ctx, ngx_str_t **params);
static ngx_int_t ngx_http_ssi_echo(ngx_http_request_t *r,
    ngx_http_ssi_ctx_t *ctx, ngx_str_t **params);
static ngx_int_t ngx_http_ssi_config(ngx_http_request_t *r,
    ngx_http_ssi_ctx_t *ctx, ngx_str_t **params);
static ngx_int_t ngx_http_ssi_set(ngx_http_request_t *r,
    ngx_http_ssi_ctx_t *ctx, ngx_str_t **params);
static ngx_int_t ngx_http_ssi_if(ngx_http_request_t *r,
    ngx_http_ssi_ctx_t *ctx, ngx_str_t **params);
static ngx_int_t ngx_http_ssi_else(ngx_http_request_t *r,
    ngx_http_ssi_ctx_t *ctx, ngx_str_t **params);
static ngx_int_t ngx_http_ssi_endif(ngx_http_request_t *r,
    ngx_http_ssi_ctx_t *ctx, ngx_str_t **params);

static ngx_int_t ngx_http_ssi_date_gmt_local_variable(ngx_http_request_t *r,
    ngx_http_variable_value_t *v,  uintptr_t gmt);

static char *ngx_http_ssi_types(ngx_conf_t *cf, ngx_command_t *cmd, void *conf);

static ngx_int_t ngx_http_ssi_add_variables(ngx_conf_t *cf);
static void *ngx_http_ssi_create_conf(ngx_conf_t *cf);
static char *ngx_http_ssi_merge_conf(ngx_conf_t *cf,
    void *parent, void *child);
static ngx_int_t ngx_http_ssi_filter_init(ngx_cycle_t *cycle);


static ngx_command_t  ngx_http_ssi_filter_commands[] = {

    { ngx_string("ssi"),
      NGX_HTTP_MAIN_CONF|NGX_HTTP_SRV_CONF|NGX_HTTP_LOC_CONF|NGX_CONF_FLAG,
      ngx_conf_set_flag_slot,
      NGX_HTTP_LOC_CONF_OFFSET,
      offsetof(ngx_http_ssi_conf_t, enable),
      NULL },

    { ngx_string("ssi_silent_errors"),
      NGX_HTTP_MAIN_CONF|NGX_HTTP_SRV_CONF|NGX_HTTP_LOC_CONF|NGX_CONF_FLAG,
      ngx_conf_set_flag_slot,
      NGX_HTTP_LOC_CONF_OFFSET,
      offsetof(ngx_http_ssi_conf_t, silent_errors),
      NULL },

    { ngx_string("ssi_ignore_recycled_buffers"),
      NGX_HTTP_MAIN_CONF|NGX_HTTP_SRV_CONF|NGX_HTTP_LOC_CONF|NGX_CONF_FLAG,
      ngx_conf_set_flag_slot,
      NGX_HTTP_LOC_CONF_OFFSET,
      offsetof(ngx_http_ssi_conf_t, ignore_recycled_buffers),
      NULL },

    { ngx_string("ssi_min_file_chunk"),
      NGX_HTTP_MAIN_CONF|NGX_HTTP_SRV_CONF|NGX_HTTP_LOC_CONF|NGX_CONF_FLAG,
      ngx_conf_set_size_slot,
      NGX_HTTP_LOC_CONF_OFFSET,
      offsetof(ngx_http_ssi_conf_t, min_file_chunk),
      NULL },

    { ngx_string("ssi_types"),
      NGX_HTTP_MAIN_CONF|NGX_HTTP_SRV_CONF|NGX_HTTP_LOC_CONF|NGX_CONF_1MORE,
      ngx_http_ssi_types,
      NGX_HTTP_LOC_CONF_OFFSET,
      0,
      NULL },

      ngx_null_command
};


static ngx_http_module_t  ngx_http_ssi_filter_module_ctx = {
    ngx_http_ssi_add_variables,            /* preconfiguration */
    NULL,                                  /* postconfiguration */

    NULL,                                  /* create main configuration */
    NULL,                                  /* init main configuration */

    NULL,                                  /* create server configuration */
    NULL,                                  /* merge server configuration */

    ngx_http_ssi_create_conf,              /* create location configuration */
    ngx_http_ssi_merge_conf                /* merge location configuration */
};  


ngx_module_t  ngx_http_ssi_filter_module = {
    NGX_MODULE_V1,
    &ngx_http_ssi_filter_module_ctx,       /* module context */
    ngx_http_ssi_filter_commands,          /* module directives */
    NGX_HTTP_MODULE,                       /* module type */
    NULL,                                  /* init master */
    ngx_http_ssi_filter_init,              /* init module */
    NULL,                                  /* init process */
    NULL,                                  /* init thread */
    NULL,                                  /* exit thread */
    NULL,                                  /* exit process */
    NULL,                                  /* exit master */
    NGX_MODULE_V1_PADDING
};


static ngx_http_output_header_filter_pt  ngx_http_next_header_filter;
static ngx_http_output_body_filter_pt    ngx_http_next_body_filter;


static u_char ngx_http_ssi_string[] = "<!--";

static ngx_str_t ngx_http_ssi_none = ngx_string("(none)");

#define  NGX_HTTP_SSI_INCLUDE_VIRTUAL  0
#define  NGX_HTTP_SSI_INCLUDE_FILE     1

#define  NGX_HTTP_SSI_ECHO_VAR         0
#define  NGX_HTTP_SSI_ECHO_DEFAULT     1

#define  NGX_HTTP_SSI_CONFIG_ERRMSG    0
#define  NGX_HTTP_SSI_CONFIG_TIMEFMT   1

#define  NGX_HTTP_SSI_SET_VAR          0
#define  NGX_HTTP_SSI_SET_VALUE        1

#define  NGX_HTTP_SSI_IF_EXPR          0


static ngx_http_ssi_param_t  ngx_http_ssi_include_params[] = {
    { ngx_string("virtual"), NGX_HTTP_SSI_INCLUDE_VIRTUAL, 0 },
    { ngx_string("file"), NGX_HTTP_SSI_INCLUDE_FILE, 0 },
    { ngx_null_string, 0, 0 }
};


static ngx_http_ssi_param_t  ngx_http_ssi_echo_params[] = {
    { ngx_string("var"), NGX_HTTP_SSI_ECHO_VAR, 1 },
    { ngx_string("default"), NGX_HTTP_SSI_ECHO_DEFAULT, 0 },
    { ngx_null_string, 0, 0 }
};


static ngx_http_ssi_param_t  ngx_http_ssi_config_params[] = {
    { ngx_string("errmsg"), NGX_HTTP_SSI_CONFIG_ERRMSG, 0 },
    { ngx_string("timefmt"), NGX_HTTP_SSI_CONFIG_TIMEFMT, 0 },
    { ngx_null_string, 0, 0 }
};


static ngx_http_ssi_param_t  ngx_http_ssi_set_params[] = {
    { ngx_string("var"), NGX_HTTP_SSI_SET_VAR, 1 },
    { ngx_string("value"), NGX_HTTP_SSI_SET_VALUE, 1 },
    { ngx_null_string, 0, 0 }
};


static ngx_http_ssi_param_t  ngx_http_ssi_if_params[] = {
    { ngx_string("expr"), NGX_HTTP_SSI_IF_EXPR, 1 },
    { ngx_null_string, 0, 0 }
};


static ngx_http_ssi_param_t  ngx_http_ssi_no_params[] = {
    { ngx_null_string, 0, 0 }
};


static ngx_http_ssi_command_t  ngx_http_ssi_commands[] = {
    { ngx_string("include"), ngx_http_ssi_include,
                       ngx_http_ssi_include_params, 0, 1 },
    { ngx_string("echo"), ngx_http_ssi_echo, ngx_http_ssi_echo_params, 0, 0 },
    { ngx_string("config"), ngx_http_ssi_config,
                       ngx_http_ssi_config_params, 0, 0 },
    { ngx_string("set"), ngx_http_ssi_set, ngx_http_ssi_set_params, 0, 0 },

    { ngx_string("if"), ngx_http_ssi_if, ngx_http_ssi_if_params, 0, 0 },
    { ngx_string("else"), ngx_http_ssi_else, ngx_http_ssi_no_params, 1, 0 },
    { ngx_string("endif"), ngx_http_ssi_endif, ngx_http_ssi_no_params, 1, 0 },

    { ngx_null_string, NULL, NULL, 0, 0 }
};


static ngx_http_variable_t  ngx_http_ssi_vars[] = {

    { ngx_string("date_local"), ngx_http_ssi_date_gmt_local_variable, 0,
      NGX_HTTP_VAR_NOCACHABLE, 0 },

    { ngx_string("date_gmt"), ngx_http_ssi_date_gmt_local_variable, 1,
      NGX_HTTP_VAR_NOCACHABLE, 0 },

    { ngx_null_string, NULL, 0, 0, 0 }
};


static ngx_int_t
ngx_http_ssi_header_filter(ngx_http_request_t *r)
{
    ngx_uint_t            i;
    ngx_str_t            *type;
    ngx_http_ssi_ctx_t   *ctx;
    ngx_http_ssi_conf_t  *conf;

    conf = ngx_http_get_module_loc_conf(r, ngx_http_ssi_filter_module);

    if (!conf->enable
        || r->headers_out.content_type.len == 0)
    {
        return ngx_http_next_header_filter(r);
    }


    type = conf->types->elts;
    for (i = 0; i < conf->types->nelts; i++) {
        if (r->headers_out.content_type.len >= type[i].len
            && ngx_strncasecmp(r->headers_out.content_type.data,
                               type[i].data, type[i].len) == 0)
        {
            goto found;
        }
    }

    return ngx_http_next_header_filter(r);


found:

    ctx = ngx_pcalloc(r->pool, sizeof(ngx_http_ssi_ctx_t));
    if (ctx == NULL) {
        return NGX_ERROR;
    }

    ngx_http_set_ctx(r, ctx, ngx_http_ssi_filter_module);


    ctx->value_len = conf->value_len;
    ctx->last_out = &ctx->out;

    ctx->output = 1;

    ctx->params.elts = ctx->params_array;
    ctx->params.size = sizeof(ngx_table_elt_t);
    ctx->params.nalloc = NGX_HTTP_SSI_PARAMS_N;
    ctx->params.pool = r->pool;

    ctx->timefmt.len = sizeof("%A, %d-%b-%Y %H:%M:%S %Z") - 1;
    ctx->timefmt.data = (u_char *) "%A, %d-%b-%Y %H:%M:%S %Z";

    ctx->errmsg.len =
              sizeof("[an error occurred while processing the directive]") - 1;
    ctx->errmsg.data = (u_char *)
                     "[an error occurred while processing the directive]";

    r->filter_need_in_memory = 1;

    if (r->main == r) {
        r->headers_out.content_length_n = -1;
        if (r->headers_out.content_length) {
            r->headers_out.content_length->hash = 0;
            r->headers_out.content_length = NULL;
        }

        r->headers_out.last_modified_time = -1;
        if (r->headers_out.last_modified) {
            r->headers_out.last_modified->hash = 0;
            r->headers_out.last_modified = NULL;
        }
    }

    return ngx_http_next_header_filter(r);
}


static ngx_int_t
ngx_http_ssi_body_filter(ngx_http_request_t *r, ngx_chain_t *in)
{
    ngx_int_t                rc;
    ngx_uint_t               i;
    ngx_buf_t               *b;
    ngx_chain_t             *cl;
    ngx_table_elt_t         *param;
    ngx_connection_t        *c;
    ngx_http_ssi_ctx_t      *ctx;
    ngx_http_ssi_conf_t     *conf;
    ngx_http_ssi_param_t    *prm;
    ngx_http_ssi_command_t  *cmd;
    ngx_str_t               *params[NGX_HTTP_SSI_MAX_PARAMS];

    ctx = ngx_http_get_module_ctx(r, ngx_http_ssi_filter_module);

    if (ctx == NULL || (in == NULL && ctx->in == NULL && ctx->busy == NULL)) {
        return ngx_http_next_body_filter(r, in);
    }

    /* add the incoming chain to the chain ctx->in */

    if (in) {
        if (ngx_chain_add_copy(r->pool, &ctx->in, in) == NGX_ERROR) {
            return NGX_ERROR;
        }
    }

    conf = ngx_http_get_module_loc_conf(r, ngx_http_ssi_filter_module);

    ngx_log_debug1(NGX_LOG_DEBUG_HTTP, r->connection->log, 0,
                   "http ssi filter \"%V\"", &r->uri);

    while (ctx->in || ctx->buf) {

        if (ctx->buf == NULL ){
            ctx->buf = ctx->in->buf;
            ctx->in = ctx->in->next;
            ctx->pos = ctx->buf->pos;
        }

        if (ctx->state == ssi_start_state) {
            ctx->copy_start = ctx->pos;
            ctx->copy_end = ctx->pos;
        }

        b = NULL;

        while (ctx->pos < ctx->buf->last) {

            ngx_log_debug2(NGX_LOG_DEBUG_HTTP, r->connection->log, 0,
                           "saved: %d state: %d", ctx->saved, ctx->state);

            rc = ngx_http_ssi_parse(r, ctx);

            ngx_log_debug4(NGX_LOG_DEBUG_HTTP, r->connection->log, 0,
                           "parse: %d, looked: %d %p-%p",
                           rc, ctx->looked, ctx->copy_start, ctx->copy_end);

            if (rc == NGX_ERROR) {
                return rc;
            }

            if (ctx->copy_start != ctx->copy_end) {

                if (ctx->output) {

                    ngx_log_debug1(NGX_LOG_DEBUG_HTTP, r->connection->log, 0,
                                   "saved: %d", ctx->saved);

                    if (ctx->saved) {

                        if (ctx->free) {
                            cl = ctx->free;
                            ctx->free = ctx->free->next;
                            b = cl->buf;
                            ngx_memzero(b, sizeof(ngx_buf_t));

                        } else {
                            b = ngx_calloc_buf(r->pool);
                            if (b == NULL) {
                                return NGX_ERROR;
                            }

                            cl = ngx_alloc_chain_link(r->pool);
                            if (cl == NULL) {
                                return NGX_ERROR;
                            }

                            cl->buf = b;
                        }

                        b->memory = 1;
                        b->pos = ngx_http_ssi_string;
                        b->last = ngx_http_ssi_string + ctx->saved;

                        *ctx->last_out = cl;
                        ctx->last_out = &cl->next;

                        ctx->saved = 0;
                    }

                    if (ctx->free) {
                        cl = ctx->free;
                        ctx->free = ctx->free->next;
                        b = cl->buf;

                    } else {
                        b = ngx_alloc_buf(r->pool);
                        if (b == NULL) {
                            return NGX_ERROR;
                        }

                        cl = ngx_alloc_chain_link(r->pool);
                        if (cl == NULL) {
                            return NGX_ERROR;
                        }

                        cl->buf = b;
                    }

                    ngx_memcpy(b, ctx->buf, sizeof(ngx_buf_t));

                    b->pos = ctx->copy_start;
                    b->last = ctx->copy_end;
                    b->shadow = NULL;
                    b->last_buf = 0;
                    b->recycled = 0;

                    if (b->in_file) {
                        if (conf->min_file_chunk < (size_t) (b->last - b->pos))
                        {
                            b->file_last = b->file_pos + (b->last - b->start);
                            b->file_pos += b->pos - b->start;

                        } else {
                            b->in_file = 0;
                        }
                    }

                    cl->next = NULL;
                    *ctx->last_out = cl;
                    ctx->last_out = &cl->next;

                } else {
                    ctx->saved = 0;
                }
            }

            if (ctx->state == ssi_start_state) {
                ctx->copy_start = ctx->pos;
                ctx->copy_end = ctx->pos;

            } else {
                ctx->copy_start = NULL;
                ctx->copy_end = NULL;
            }

            if (rc == NGX_AGAIN) {
                continue;
            }


            b = NULL;

            if (rc == NGX_OK) {

                for (cmd = ngx_http_ssi_commands; cmd->handler; cmd++) {
                    if (cmd->name.len == 0) {
                        cmd = (ngx_http_ssi_command_t *) cmd->handler;
                    }

                    if (cmd->name.len != ctx->command.len
                        || ngx_strncmp(cmd->name.data, ctx->command.data,
                                       ctx->command.len) != 0)
                    {
                        continue;
                    }

                    break;
                }

                if (cmd->name.len == 0 && ctx->output) {
                    ngx_log_error(NGX_LOG_ERR, r->connection->log, 0,
                                  "invalid SSI command: \"%V\"", &ctx->command);
                    goto ssi_error;
                }

                if (!ctx->output && !cmd->conditional) {
                    continue;
                }

                ngx_memzero(params,
                            NGX_HTTP_SSI_MAX_PARAMS * sizeof(ngx_str_t *));

                param = ctx->params.elts;


                for (i = 0; i < ctx->params.nelts; i++) {

                    for (prm = cmd->params; prm->name.len; prm++) {

                        if (param[i].key.len != prm->name.len
                            || ngx_strncmp(param[i].key.data, prm->name.data,
                                           prm->name.len) != 0)
                        {
                            continue;
                        }

                        if (params[prm->index]) {
                            ngx_log_error(NGX_LOG_ERR,
                                          r->connection->log, 0,
                                          "duplicate \"%V\" parameter "
                                          "in \"%V\" SSI command",
                                          &param[i].key, &ctx->command);

                            goto ssi_error;
                        }

                        params[prm->index] = &param[i].value;

                        break;
                    }

                    if (prm->name.len == 0) {
                        ngx_log_error(NGX_LOG_ERR, r->connection->log, 0,
                                      "invalid parameter name: \"%V\" "
                                      "in \"%V\" SSI command",
                                      &param[i].key, &ctx->command);

                        goto ssi_error;
                    }
                }

                for (prm = cmd->params; prm->name.len; prm++) {
                    if (prm->mandatory && params[prm->index] == 0) {
                        ngx_log_error(NGX_LOG_ERR, r->connection->log, 0,
                                      "mandatory \"%V\" parameter is absent "
                                      "in \"%V\" SSI command",
                                      &prm->name, &ctx->command);

                        goto ssi_error;
                    }
                }

                if (cmd->flush && ctx->out) {
                    rc = ngx_http_ssi_output(r, ctx);

                    if (rc == NGX_ERROR) {
                        return NGX_ERROR;
                    }
                }

                c = r->connection;

                rc = cmd->handler(r, ctx, params);

                if (c->closed) {
                    return NGX_DONE;
                }

                if (rc == NGX_OK) {
                    continue;
                }
            }


            /* rc == NGX_HTTP_SSI_ERROR */

    ssi_error:

            if (conf->silent_errors) {
                continue;
            }

            if (ctx->free) {
                cl = ctx->free;
                ctx->free = ctx->free->next;
                b = cl->buf;
                ngx_memzero(b, sizeof(ngx_buf_t));

            } else {
                b = ngx_calloc_buf(r->pool);
                if (b == NULL) {
                    return NGX_ERROR;
                }

                cl = ngx_alloc_chain_link(r->pool);
                if (cl == NULL) {
                    return NGX_ERROR;
                }

                cl->buf = b;
            }

            b->memory = 1;
            b->pos = ctx->errmsg.data;
            b->last = ctx->errmsg.data + ctx->errmsg.len;

            cl->next = NULL;
            *ctx->last_out = cl;
            ctx->last_out = &cl->next;

            continue;
        }

        if (ctx->buf->last_buf || ctx->buf->recycled) {

            if (b == NULL) {
                if (ctx->free) {
                    cl = ctx->free;
                    ctx->free = ctx->free->next;
                    b = cl->buf;
                    ngx_memzero(b, sizeof(ngx_buf_t));

                } else {
                    b = ngx_calloc_buf(r->pool);
                    if (b == NULL) {
                        return NGX_ERROR;
                    }

                    cl = ngx_alloc_chain_link(r->pool);
                    if (cl == NULL) {
                        return NGX_ERROR;
                    }

                    cl->buf = b;
                }

                b->sync = 1;

                cl->next = NULL;
                *ctx->last_out = cl;
                ctx->last_out = &cl->next;
            }

            b->last_buf = ctx->buf->last_buf;
            b->shadow = ctx->buf;

            if (conf->ignore_recycled_buffers == 0)  {
                b->recycled = ctx->buf->recycled;
            }
        }

        ctx->buf = NULL;

        ctx->saved = ctx->looked;
    }

    if (ctx->out == NULL && ctx->busy == NULL) {
        return NGX_OK;
    }

    return ngx_http_ssi_output(r, ctx);
}


static ngx_int_t
ngx_http_ssi_output(ngx_http_request_t *r, ngx_http_ssi_ctx_t *ctx)
{
    ngx_int_t     rc;
    ngx_buf_t    *b;
    ngx_chain_t  *cl;

    rc = ngx_http_next_body_filter(r, ctx->out);

    if (ctx->busy == NULL) {
        ctx->busy = ctx->out;

    } else {
        for (cl = ctx->busy; cl->next; cl = cl->next) { /* void */ }
        cl->next = ctx->out;
    }

    ctx->out = NULL;
    ctx->last_out = &ctx->out;

    while (ctx->busy) {

        b = ctx->busy->buf;

        if (ngx_buf_size(b) != 0) {
            break;
        }

#if (NGX_HAVE_WRITE_ZEROCOPY)
        if (b->zerocopy_busy) {
            break;
        }
#endif

        if (b->shadow) {
            b->shadow->pos = b->shadow->last;
        }

        cl = ctx->busy;
        ctx->busy = cl->next;
        cl->next = ctx->free;
        ctx->free = cl;
    }

    return rc;
}


static ngx_int_t
ngx_http_ssi_parse(ngx_http_request_t *r, ngx_http_ssi_ctx_t *ctx)
{
    u_char                *p, *last, *copy_end, ch;
    size_t                 looked;
    ngx_http_ssi_state_e   state;

    state = ctx->state;
    looked = ctx->looked;
    last = ctx->buf->last;
    copy_end = ctx->copy_end;

    for (p = ctx->pos; p < last; p++) {

        ch = *p;

        if (state == ssi_start_state) {

            /* the tight loop */

            for ( ;; ) {
                if (ch == '<') {
                    copy_end = p;
                    looked = 1;
                    state = ssi_tag_state;

                    goto tag_started;
                }

                if (++p == last) {
                    break;
                }

                ch = *p;
            }

            ctx->pos = p;
            ctx->looked = looked;
            ctx->copy_end = p;

            if (ctx->copy_start == NULL) {
                ctx->copy_start = ctx->buf->pos;
            }

            return NGX_AGAIN;

        tag_started:

            continue;
        }

        switch (state) {

        case ssi_start_state:
            break;

        case ssi_tag_state:
            switch (ch) {
            case '!':
                looked = 2;
                state = ssi_comment0_state;
                break;

            case '<':
                copy_end = p;
                break;

            default:
                copy_end = p;
                looked = 0;
                state = ssi_start_state;
                break;
            }

            break;

        case ssi_comment0_state:
            switch (ch) {
            case '-':
                looked = 3;
                state = ssi_comment1_state;
                break;

            case '<':
                copy_end = p;
                looked = 1;
                state = ssi_tag_state;
                break;

            default:
                copy_end = p;
                looked = 0;
                state = ssi_start_state;
                break;
            }

            break;

        case ssi_comment1_state:
            switch (ch) {
            case '-':
                looked = 4;
                state = ssi_sharp_state;
                break;

            case '<':
                copy_end = p;
                looked = 1;
                state = ssi_tag_state;
                break;

            default:
                copy_end = p;
                looked = 0;
                state = ssi_start_state;
                break;
            }

            break;

        case ssi_sharp_state:
            switch (ch) {
            case '#':
                if (ctx->copy_start) {
                    ctx->saved = 0;
                }
                looked = 0;
                state = ssi_precommand_state;
                break;

            case '<':
                copy_end = p;
                looked = 1;
                state = ssi_tag_state;
                break;

            default:
                copy_end = p;
                looked = 0;
                state = ssi_start_state;
                break;
            }

            break;

        case ssi_precommand_state:
            switch (ch) {
            case ' ':
            case CR:
            case LF:
            case '\t':
                break;

            default:
                ctx->command.len = 1;
                ctx->command.data = ngx_palloc(r->pool,
                                               NGX_HTTP_SSI_COMMAND_LEN + 1);
                if (ctx->command.data == NULL) {
                    return NGX_ERROR;
                }

                ctx->command.data[0] = ch;
                ctx->params.nelts = 0;
                state = ssi_command_state;
                break;
            }

            break;

        case ssi_command_state:
            switch (ch) {
            case ' ':
            case CR:
            case LF:
            case '\t':
                state = ssi_preparam_state;
                break;

            case '-':
                state = ssi_comment_end0_state;
                break;

            default:
                ctx->command.data[ctx->command.len++] = ch;

                if (ctx->command.len == NGX_HTTP_SSI_COMMAND_LEN) {
                    ngx_log_error(NGX_LOG_ERR, r->connection->log, 0,
                                  "the \"%V\" SSI command is too long",
                                  &ctx->command);

                    state = ssi_error_state;
                    break;
                }
            }

            break;

        case ssi_preparam_state:
            switch (ch) {
            case ' ':
            case CR:
            case LF:
            case '\t':
                break;

            case '-':
                state = ssi_comment_end0_state;
                break;

            default:
                ctx->param = ngx_array_push(&ctx->params);
                if (ctx->param == NULL) {
                    return NGX_ERROR;
                }

                ctx->param->key.len = 1;
                ctx->param->key.data = ngx_palloc(r->pool,
                                                  NGX_HTTP_SSI_PARAM_LEN + 1);
                if (ctx->param->key.data == NULL) {
                    return NGX_ERROR;
                }

                ctx->param->key.data[0] = ch;

                ctx->param->value.len = 0;
                ctx->param->value.data = ngx_palloc(r->pool,
                                                    ctx->value_len + 1);
                if (ctx->param->value.data == NULL) {
                    return NGX_ERROR;
                }

                state = ssi_param_state;
                break;
            }

            break;

        case ssi_param_state:
            switch (ch) {
            case ' ':
            case CR:
            case LF:
            case '\t':
                state = ssi_preequal_state;
                break;

            case '=':
                state = ssi_prevalue_state;
                break;

            case '-':
                state = ssi_error_end0_state;

                ctx->param->key.data[ctx->param->key.len++] = ch;
                ngx_log_error(NGX_LOG_ERR, r->connection->log, 0,
                              "invalid \"%V\" parameter in \"%V\" SSI command",
                              &ctx->param->key, &ctx->command);
                break;

            default:
                ctx->param->key.data[ctx->param->key.len++] = ch;

                if (ctx->param->key.len == NGX_HTTP_SSI_PARAM_LEN) {
                    state = ssi_error_state;
                    ngx_log_error(NGX_LOG_ERR, r->connection->log, 0,
                                  "too long \"%V\" parameter in "
                                  "\"%V\" SSI command",
                                  &ctx->param->key, &ctx->command);
                    break;
                }
            }

            break;

        case ssi_preequal_state:
            switch (ch) {
            case ' ':
            case CR:
            case LF:
            case '\t':
                break;

            case '=':
                state = ssi_prevalue_state;
                break;

            default:
                if (ch == '-') {
                    state = ssi_error_end0_state;
                } else {
                    state = ssi_error_state;
                }

                ngx_log_error(NGX_LOG_ERR, r->connection->log, 0,
                              "unexpected \"%c\" symbol after \"%V\" "
                              "parameter in \"%V\" SSI command",
                              ch, &ctx->param->key, &ctx->command);
                break;
            }

            break;

        case ssi_prevalue_state:
            switch (ch) {
            case ' ':
            case CR:
            case LF:
            case '\t':
                break;

            case '"':
                state = ssi_double_quoted_value_state;
                break;

            case '\'':
                state = ssi_quoted_value_state;
                break;

            default:
                if (ch == '-') {
                    state = ssi_error_end0_state;
                } else {
                    state = ssi_error_state;
                }

                ngx_log_error(NGX_LOG_ERR, r->connection->log, 0,
                              "unexpected \"%c\" symbol before value of "
                              "\"%V\" parameter in \"%V\" SSI command",
                              ch, &ctx->param->key, &ctx->command);
                break;
            }

            break;

        case ssi_double_quoted_value_state:
            switch (ch) {
            case '"':
                state = ssi_postparam_state;
                break;

            case '\\':
                ctx->saved_state = ssi_double_quoted_value_state;
                state = ssi_quoted_symbol_state;

                /* fall through */

            default:
                ctx->param->value.data[ctx->param->value.len++] = ch;

                if (ctx->param->value.len == ctx->value_len) {
                    ngx_log_error(NGX_LOG_ERR, r->connection->log, 0,
                                  "too long \"%V\" value of \"%V\" parameter "
                                  "in \"%V\" SSI command",
                                  &ctx->param->value, &ctx->param->key,
                                  &ctx->command);
                    state = ssi_error_state;
                    break;
                }
            }

            break;

        case ssi_quoted_value_state:
            switch (ch) {
            case '\'':
                state = ssi_postparam_state;
                break;

            case '\\':
                ctx->saved_state = ssi_quoted_value_state;
                state = ssi_quoted_symbol_state;

                /* fall through */

            default:
                ctx->param->value.data[ctx->param->value.len++] = ch;

                if (ctx->param->value.len == ctx->value_len) {
                    ngx_log_error(NGX_LOG_ERR, r->connection->log, 0,
                                  "too long \"%V\" value of \"%V\" parameter "
                                  "in \"%V\" SSI command",
                                  &ctx->param->value, &ctx->param->key,
                                  &ctx->command);
                    state = ssi_error_state;
                    break;
                }
            }

            break;

        case ssi_quoted_symbol_state:
            state = ctx->saved_state;

            if (ch == '\\') {
                break;
            }

            if (ch == '"' && state == ssi_double_quoted_value_state) {
                ctx->param->value.data[ctx->param->value.len - 1] = ch;
                break;
            }

            if (ch == '\'' && state == ssi_quoted_value_state) {
                ctx->param->value.data[ctx->param->value.len - 1] = ch;
                break;
            }

            ctx->param->value.data[ctx->param->value.len++] = ch;

            if (ctx->param->value.len == ctx->value_len) {
                if (ctx->param->value.len == ctx->value_len) {
                    ngx_log_error(NGX_LOG_ERR, r->connection->log, 0,
                                  "too long \"%V\" value of \"%V\" parameter "
                                  "in \"%V\" SSI command",
                                  &ctx->param->value, &ctx->param->key,
                                  &ctx->command);
                    state = ssi_error_state;
                    break;
                }
            }

            break;

        case ssi_postparam_state:
            switch (ch) {
            case ' ':
            case CR:
            case LF:
            case '\t':
                state = ssi_preparam_state;
                break;

            case '-':
                state = ssi_comment_end0_state;
                break;

            default:
                ngx_log_error(NGX_LOG_ERR, r->connection->log, 0,
                              "unexpected \"%c\" symbol after \"%V\" value "
                              "of \"%V\" parameter in \"%V\" SSI command",
                              ch, &ctx->param->value, &ctx->param->key,
                              &ctx->command);
                state = ssi_error_state;
                break;
            }

            break;

        case ssi_comment_end0_state:
            switch (ch) {
            case '-':
                state = ssi_comment_end1_state;
                break;

            default:
                ngx_log_error(NGX_LOG_ERR, r->connection->log, 0,
                              "unexpected \"%c\" symbol in \"%V\" SSI command",
                              ch, &ctx->command);
                state = ssi_error_state;
                break;
            }

            break;

        case ssi_comment_end1_state:
            switch (ch) {
            case '>':
                ctx->state = ssi_start_state;
                ctx->pos = p + 1;
                ctx->looked = looked;
                ctx->copy_end = copy_end;

                if (ctx->copy_start == NULL && copy_end) {
                    ctx->copy_start = ctx->buf->pos;
                }

                return NGX_OK;

            default:
                ngx_log_error(NGX_LOG_ERR, r->connection->log, 0,
                              "unexpected \"%c\" symbol in \"%V\" SSI command",
                              ch, &ctx->command);
                state = ssi_error_state;
                break;
            }

            break;

        case ssi_error_state:
            switch (ch) {
            case '-':
                state = ssi_error_end0_state;
                break;

            default:
                break;
            }

            break;

        case ssi_error_end0_state:
            switch (ch) {
            case '-':
                state = ssi_error_end1_state;
                break;

            default:
                state = ssi_error_state;
                break;
            }

            break;

        case ssi_error_end1_state:
            switch (ch) {
            case '>':
                ctx->state = ssi_start_state;
                ctx->pos = p + 1;
                ctx->looked = looked;
                ctx->copy_end = copy_end;

                if (ctx->copy_start == NULL && copy_end) {
                    ctx->copy_start = ctx->buf->pos;
                }

                return NGX_HTTP_SSI_ERROR;

            default:
                state = ssi_error_state;
                break;
            }

            break;
        }
    }

    ctx->state = state;
    ctx->pos = p;
    ctx->looked = looked;

    ctx->copy_end = (state == ssi_start_state) ? p : copy_end;

    if (ctx->copy_start == NULL && ctx->copy_end) {
        ctx->copy_start = ctx->buf->pos;
    }

    return NGX_AGAIN;
}


static ngx_str_t *
ngx_http_ssi_get_variable(ngx_http_request_t *r, ngx_str_t *name)
{
    ngx_uint_t           i;
    ngx_http_ssi_var_t  *var;
    ngx_http_ssi_ctx_t  *ctx;

    ctx = ngx_http_get_module_ctx(r->main, ngx_http_ssi_filter_module);

    var = ctx->variables.elts;
    for (i = 0; i < ctx->variables.nelts; i++) {
        if (name->len != var[i].name.len) {
            continue;
        }

        if (ngx_strncasecmp(name->data, var[i].name.data, name->len) == 0) {
            return &var[i].value;
        }
    }

    return NULL;
}


static ngx_int_t
ngx_http_ssi_evaluate_string(ngx_http_request_t *r, ngx_http_ssi_ctx_t *ctx,
    ngx_str_t *text, ngx_uint_t flags)
{
    u_char                      ch, *p, **value, *data, *part_data;
    size_t                     *size, len, prefix, part_len;
    ngx_str_t                   var, *val;
    ngx_uint_t                  i, j, n, bracket;
    ngx_array_t                 lengths, values;
    ngx_http_variable_value_t  *vv;

    n = ngx_http_script_variables_count(text);

    if (n == 0) {

        if (!(flags & NGX_HTTP_SSI_ADD_PREFIX)) {
            return NGX_OK;
        }

        if (text->data[0] != '/') {
            for (prefix = r->uri.len; prefix; prefix--) {
                if (r->uri.data[prefix - 1] == '/') {
                    break;
                }
            }

            if (prefix) {
                len = prefix + text->len;

                data = ngx_palloc(r->pool, len);
                if (data == NULL) {
                    return NGX_ERROR;
                }

                p = ngx_copy(data, r->uri.data, prefix);
                ngx_memcpy(p, text->data, text->len);

                text->len = len;
                text->data = data;
            }
        }

        return NGX_OK;
    }

    if (ngx_array_init(&lengths, r->pool, 8, sizeof(size_t *)) != NGX_OK) {
        return NGX_ERROR;
    }

    if (ngx_array_init(&values, r->pool, 8, sizeof(u_char *)) != NGX_OK) {
        return NGX_ERROR;
    }

    len = 0;
    i = 0;

    while (i < text->len) {

        if (text->data[i] == '$') {

            var.len = 0;

            if (++i == text->len) {
                goto invalid_variable;
            }

            if (text->data[i] == '{') {
                bracket = 1;

                if (++i == text->len) {
                    goto invalid_variable;
                }

                var.data = &text->data[i];

            } else {
                bracket = 0;
                var.data = &text->data[i];
            }

            for ( /* void */ ; i < text->len; i++, var.len++) {
                ch = text->data[i];

                if (ch == '}' && bracket) {
                    i++;
                    bracket = 0;
                    break;
                }

                if ((ch >= 'A' && ch <= 'Z')
                    || (ch >= 'a' && ch <= 'z')
                    || (ch >= '0' && ch <= '9')
                    || ch == '_')
                {
                    continue;
                }

                break;
            }

            if (bracket) {
                ngx_log_error(NGX_LOG_ERR, r->connection->log, 0,
                              "the closing bracket in \"%V\" "
                              "variable is missing", &var);
                return NGX_ERROR;
            }

            if (var.len == 0) { 
                goto invalid_variable;
            }

            for (j = 0; j < var.len; j++) {
                var.data[j] = ngx_tolower(var.data[j]);
            }

            val = ngx_http_ssi_get_variable(r, &var);

            if (val == NULL) {
                vv = ngx_http_get_variable(r, &var);

                if (vv == NULL) {
                    return NGX_ERROR;
                }

                if (vv->not_found) {
                    continue;
                }

                part_data = vv->data;
                part_len = vv->len;

            } else {
                part_data = val->data;
                part_len = val->len;
            }

        } else {
            part_data = &text->data[i];

            for (p = part_data; i < text->len; i++) {
                ch = text->data[i];

                if (ch == '$') {
                    if (text->data[i - 1] != '\\') {
                        break;
                    }

                    *(p - 1) = ch;

                    continue;
                }

                *p++ = ch;
            }

            part_len = p - part_data;
        }

        len += part_len;

        size = ngx_array_push(&lengths);
        if (size == NULL) {
            return NGX_ERROR;
        }

        *size = part_len;

        value = ngx_array_push(&values);
        if (value == NULL) {
            return NGX_ERROR;
        }

        *value = part_data;
    }

    prefix = 0;

    size = lengths.elts;
    value = values.elts;

    if (flags & NGX_HTTP_SSI_ADD_PREFIX) {
        for (i = 0; i < values.nelts; i++) {
            if (size[i] != 0) {
                if (*value[i] != '/') {
                    for (prefix = r->uri.len; prefix; prefix--) {
                        if (r->uri.data[prefix - 1] == '/') {
                            len += prefix;
                            break;
                        }
                    }
                }

                break;
            }
        }
    }

    p = ngx_palloc(r->pool, len);
    if (p == NULL) {
        return NGX_ERROR;
    }

    text->len = len;
    text->data = p;

    p = ngx_copy(p, r->uri.data, prefix);

    for (i = 0; i < values.nelts; i++) {
        p = ngx_copy(p, value[i], size[i]);
    }

    return NGX_OK;

invalid_variable:

    ngx_log_error(NGX_LOG_ERR, r->connection->log, 0,
                  "invalid variable name in \"%V\"", text);

    return NGX_ERROR;
}


static ngx_int_t
ngx_http_ssi_include(ngx_http_request_t *r, ngx_http_ssi_ctx_t *ctx,
    ngx_str_t **params)
{
    ngx_str_t   *uri, *file, args;
    ngx_uint_t   flags;

    uri = params[NGX_HTTP_SSI_INCLUDE_VIRTUAL];
    file = params[NGX_HTTP_SSI_INCLUDE_FILE];

    if (uri && file) {
        ngx_log_error(NGX_LOG_ERR, r->connection->log, 0,
                      "inlcusion may be either virtual=\"%V\" or file=\"%V\"",
                      uri, file);
        return NGX_HTTP_SSI_ERROR;
    }

    if (uri == NULL && file == NULL) {
        ngx_log_error(NGX_LOG_ERR, r->connection->log, 0,
                      "no parameter in \"include\" SSI command");
        return NGX_HTTP_SSI_ERROR;
    }

    if (uri == NULL) {
        uri = file;
    }

    if (ngx_http_ssi_evaluate_string(r, ctx, uri, NGX_HTTP_SSI_ADD_PREFIX)
        != NGX_OK)
    {
        return NGX_HTTP_SSI_ERROR;
    }

    args.len = 0;
    args.data = NULL;
    flags = 0;

    ngx_log_debug1(NGX_LOG_DEBUG_HTTP, r->connection->log, 0,
                   "ssi include: \"%V\"", uri);

    if (ngx_http_parse_unsafe_uri(r, uri, &args, &flags) != NGX_OK) {
        return NGX_HTTP_SSI_ERROR;
    }

    if (ngx_http_subrequest(r, uri, &args, flags) != NGX_OK) {
        return NGX_HTTP_SSI_ERROR;
    }

    return NGX_OK;
}


static ngx_int_t
ngx_http_ssi_echo(ngx_http_request_t *r, ngx_http_ssi_ctx_t *ctx,
    ngx_str_t **params)
{
    ngx_uint_t                  i;
    ngx_buf_t                  *b;
    ngx_str_t                  *var, *value, text;
    ngx_chain_t                *cl;
    ngx_http_variable_value_t  *vv;

    var = params[NGX_HTTP_SSI_ECHO_VAR];

    value = ngx_http_ssi_get_variable(r, var);

    if (value == NULL) {
        for (i = 0; i < var->len; i++) {
            var->data[i] = ngx_tolower(var->data[i]);
        }

        vv = ngx_http_get_variable(r, var);

        if (vv == NULL) {
            return NGX_HTTP_SSI_ERROR;
        }

        if (!vv->not_found) {
            text.data = vv->data;
            text.len = vv->len;
            value = &text;
        }
    }

    if (value == NULL) {
        value = params[NGX_HTTP_SSI_ECHO_DEFAULT];

        if (value == NULL) {
            value = &ngx_http_ssi_none;

        } else if (value->len == 0) {
            return NGX_OK;
        }

    } else {
        if (value->len == 0) {
            return NGX_OK;
        }
    }

    b = ngx_calloc_buf(r->pool);
    if (b == NULL) {
        return NGX_HTTP_SSI_ERROR;
    }

    cl = ngx_alloc_chain_link(r->pool);
    if (cl == NULL) {
        return NGX_HTTP_SSI_ERROR;
    }

    b->memory = 1;
    b->pos = value->data;
    b->last = value->data + value->len;

    cl->buf = b;
    cl->next = NULL;
    *ctx->last_out = cl;
    ctx->last_out = &cl->next;

    return NGX_OK;
}


static ngx_int_t
ngx_http_ssi_config(ngx_http_request_t *r, ngx_http_ssi_ctx_t *ctx,
    ngx_str_t **params)
{
    ngx_str_t  *value;

    value = params[NGX_HTTP_SSI_CONFIG_TIMEFMT];

    if (value) {
        ctx->timefmt = *value;
    }

    value = params[NGX_HTTP_SSI_CONFIG_ERRMSG];

    if (value) {
        ctx->errmsg = *value;
    }

    return NGX_OK;
}


static ngx_int_t
ngx_http_ssi_set(ngx_http_request_t *r, ngx_http_ssi_ctx_t *ctx,
    ngx_str_t **params)
{
    ngx_str_t           *name, *value, *vv;
    ngx_http_ssi_var_t  *var;
    ngx_http_ssi_ctx_t  *mctx;

    mctx = ngx_http_get_module_ctx(r->main, ngx_http_ssi_filter_module);

    if (mctx->variables.elts == NULL) {
        if (ngx_array_init(&mctx->variables, r->pool, 4,
                           sizeof(ngx_http_ssi_var_t)) != NGX_OK)
        {
            return NGX_HTTP_SSI_ERROR;
        }
    }

    name = params[NGX_HTTP_SSI_SET_VAR];
    value = params[NGX_HTTP_SSI_SET_VALUE];

    if (ngx_http_ssi_evaluate_string(r, ctx, value, 0) != NGX_OK) {
        return NGX_HTTP_SSI_ERROR;
    }

    vv = ngx_http_ssi_get_variable(r, name);

    if (vv) {
        *vv = *value;
        return NGX_OK;
    }

    var = ngx_array_push(&mctx->variables);
    if (var == NULL) {
        return NGX_HTTP_SSI_ERROR;
    }

    var->name = *name;
    var->value = *value;

    ngx_log_debug2(NGX_LOG_DEBUG_HTTP, r->connection->log, 0,
                   "set: \"%V\"=\"%V\"", name, value);

    return NGX_OK;
}


static ngx_int_t
ngx_http_ssi_if(ngx_http_request_t *r, ngx_http_ssi_ctx_t *ctx,
    ngx_str_t **params)
{
    u_char       *p, *last;
    ngx_str_t    *expr, left, right;
    ngx_int_t     rc;
    ngx_uint_t    negative, noregex;
#if (NGX_PCRE)
    ngx_str_t     err;
    ngx_regex_t  *regex;
    u_char        errstr[NGX_MAX_CONF_ERRSTR];
#endif

    expr = params[NGX_HTTP_SSI_IF_EXPR];

    left.data = expr->data;
    last = expr->data + expr->len;

    for (p = left.data; p < last; p++) {
        if (*p >= 'A' && *p <= 'Z') {
            *p |= 0x20;
            continue;
        }

        if ((*p >= 'a' && *p <= 'z')
             || (*p >= '0' && *p <= '9')
             || *p == '$' || *p == '{' || *p == '}' || *p == '_'
             || *p == '"' || *p == '\'')
        {
            continue;
        }

        break;
    }

    left.len = p - left.data;

    while (p < last && *p == ' ') {
        p++;
    }

    ngx_log_debug1(NGX_LOG_DEBUG_HTTP, r->connection->log, 0,
                   "left: \"%V\"", &left);

    if (ngx_http_ssi_evaluate_string(r, ctx, &left, 0) != NGX_OK) {
        return NGX_HTTP_SSI_ERROR;
    }

    ngx_log_debug1(NGX_LOG_DEBUG_HTTP, r->connection->log, 0,
                   "evaluted left: \"%V\"", &left);

    if (p == last) {
        if (left.len) {
            ctx->output = 1;

        } else {
            ctx->output = 0;
        }

        return NGX_OK;
    }

    if (p < last && *p == '=') {
        negative = 0;
        p++;

    } else if (p + 1 < last && *p == '!' && *(p + 1) == '=') {
        negative = 1;
        p += 2;

    } else {
        goto invalid_expression;
    }

    while (p < last && *p == ' ') {
        p++;
    }

    if (p < last && *p == '/') {
        if (*(last - 1) != '/') {
            goto invalid_expression;
        }

        noregex = 0;
        last--;
	p++;

    } else {
        noregex = 1;
    }

    right.len = last - p;
    right.data = p;

    ngx_log_debug1(NGX_LOG_DEBUG_HTTP, r->connection->log, 0,
                   "right: \"%V\"", &right);

    if (ngx_http_ssi_evaluate_string(r, ctx, &right, 0) != NGX_OK) {
        return NGX_HTTP_SSI_ERROR;
    }

    ngx_log_debug1(NGX_LOG_DEBUG_HTTP, r->connection->log, 0,
                   "evaluted right: \"%V\"", &right);

    if (noregex) {
        if (left.len != right.len) {
            rc = -1;

        } else {
            rc = ngx_strncmp(left.data, right.data, right.len);
        }

    } else {
#if (NGX_PCRE)
        err.len = NGX_MAX_CONF_ERRSTR;
        err.data = errstr;

        right.data[right.len] = '\0';

        regex = ngx_regex_compile(&right, 0, r->pool, &err);

        if (regex == NULL) {
            ngx_log_error(NGX_LOG_ERR, r->connection->log, 0, "%s", err.data);
            return NGX_HTTP_SSI_ERROR;
        }

        rc = ngx_regex_exec(regex, &left, NULL, 0);

        if (rc != NGX_REGEX_NO_MATCHED && rc < 0) {
            ngx_log_error(NGX_LOG_ALERT, r->connection->log, 0,
                          ngx_regex_exec_n " failed: %d on \"%V\" using \"%V\"",
                          rc, &left, &right);
            return NGX_HTTP_SSI_ERROR;
        }
#else
        ngx_log_error(NGX_LOG_ALERT, r->connection->log, 0,
                      "the using of the regex \"%V\" in SSI "
                      "requires PCRE library", &right);

        return NGX_HTTP_SSI_ERROR;
#endif
    }

    if ((rc == 0 && !negative) || (rc != 0 && negative)) {
        ctx->output = 1;

    } else {
        ctx->output = 0;
    }

    return NGX_OK;

invalid_expression:

    ngx_log_error(NGX_LOG_ERR, r->connection->log, 0,
                  "invalid expression in \"%V\"", expr);

    return NGX_HTTP_SSI_ERROR;
}


static ngx_int_t
ngx_http_ssi_else(ngx_http_request_t *r, ngx_http_ssi_ctx_t *ctx,
    ngx_str_t **params)
{
    ctx->output = !ctx->output;

    return NGX_OK;
}


static ngx_int_t
ngx_http_ssi_endif(ngx_http_request_t *r, ngx_http_ssi_ctx_t *ctx,
    ngx_str_t **params)
{
    ctx->output = 1;

    return NGX_OK;
}


static ngx_int_t
ngx_http_ssi_date_gmt_local_variable(ngx_http_request_t *r,
    ngx_http_variable_value_t *v,  uintptr_t gmt)
{
    ngx_http_ssi_ctx_t  *ctx;
    ngx_time_t          *tp;
    struct tm            tm;
    char                 buf[NGX_HTTP_SSI_DATE_LEN];

    v->valid = 1; 
    v->no_cachable = 0;
    v->not_found = 0;

    tp = ngx_timeofday();

    ctx = ngx_http_get_module_ctx(r, ngx_http_ssi_filter_module);

    if (ctx->timefmt.len == sizeof("%s") - 1
        && ctx->timefmt.data[0] == '%' && ctx->timefmt.data[1] == 's')
    {
        v->data = ngx_palloc(r->pool, NGX_TIME_T_LEN);
        if (v->data == NULL) {
            return NGX_ERROR;
        }

        v->len = ngx_sprintf(v->data, "%T", tp->sec + (gmt ? 0 : tp->gmtoff))
                 - v->data;
        return NGX_OK;
    }

    if (gmt) {
        ngx_libc_gmtime(tp->sec, &tm);
    } else {
        ngx_libc_localtime(tp->sec, &tm);
    }

    v->len = strftime(buf, NGX_HTTP_SSI_DATE_LEN,
                      (char *) ctx->timefmt.data, &tm);
    if (v->len == 0) {
        return NGX_ERROR;
    }

    v->data = ngx_palloc(r->pool, v->len);
    if (v->data == NULL) {
        return NGX_ERROR;
    }

    ngx_memcpy(v->data, buf, v->len);

    return NGX_OK;
}


static char *
ngx_http_ssi_types(ngx_conf_t *cf, ngx_command_t *cmd, void *conf)
{
    ngx_http_ssi_conf_t *scf = conf;

    ngx_str_t   *value, *type;
    ngx_uint_t   i;

    if (scf->types == NULL) {
        scf->types = ngx_array_create(cf->pool, 4, sizeof(ngx_str_t));
        if (scf->types == NULL) {
            return NGX_CONF_ERROR;
        }

        type = ngx_array_push(scf->types);
        if (type == NULL) {
            return NGX_CONF_ERROR;
        }

        type->len = sizeof("text/html") - 1;
        type->data = (u_char *) "text/html";
    }

    value = cf->args->elts;

    for (i = 1; i < cf->args->nelts; i++) {

        if (ngx_strcmp(value[i].data, "text/html") == 0) {
            continue;
        }

        type = ngx_array_push(scf->types);
        if (type == NULL) {
            return NGX_CONF_ERROR;
        }

        type->len = value[i].len;

        type->data = ngx_palloc(cf->pool, type->len + 1);
        if (type->data == NULL) {
            return NGX_CONF_ERROR;
        }

        ngx_cpystrn(type->data, value[i].data, type->len + 1);
    }

    return NGX_CONF_OK;
}


static ngx_int_t
ngx_http_ssi_add_variables(ngx_conf_t *cf)
{
    ngx_http_variable_t  *var, *v;

    for (v = ngx_http_ssi_vars; v->name.len; v++) {
        var = ngx_http_add_variable(cf, &v->name, v->flags);
        if (var == NULL) {
            return NGX_ERROR;
        }

        var->handler = v->handler;
        var->data = v->data;
    }

    return NGX_OK; 
}


static void *
ngx_http_ssi_create_conf(ngx_conf_t *cf)
{
    ngx_http_ssi_conf_t  *conf;

    conf = ngx_pcalloc(cf->pool, sizeof(ngx_http_ssi_conf_t));
    if (conf == NULL) {
        return NGX_CONF_ERROR;
    }

    /*
     * set by ngx_pcalloc():
     *
     *     conf->types = NULL;
     */

    conf->enable = NGX_CONF_UNSET;
    conf->silent_errors = NGX_CONF_UNSET;
    conf->ignore_recycled_buffers = NGX_CONF_UNSET;

    conf->min_file_chunk = NGX_CONF_UNSET_SIZE;
    conf->value_len = NGX_CONF_UNSET_SIZE;

    return conf;
}


static char *
ngx_http_ssi_merge_conf(ngx_conf_t *cf, void *parent, void *child)
{
    ngx_http_ssi_conf_t *prev = parent;
    ngx_http_ssi_conf_t *conf = child;

    ngx_str_t  *type;

    ngx_conf_merge_value(conf->enable, prev->enable, 0);
    ngx_conf_merge_value(conf->silent_errors, prev->silent_errors, 0);
    ngx_conf_merge_value(conf->ignore_recycled_buffers,
                         prev->ignore_recycled_buffers, 0);

    ngx_conf_merge_size_value(conf->min_file_chunk, prev->min_file_chunk, 1024);
    ngx_conf_merge_size_value(conf->value_len, prev->value_len, 256);

    if (conf->types == NULL) {
        if (prev->types == NULL) {
            conf->types = ngx_array_create(cf->pool, 1, sizeof(ngx_str_t));
            if (conf->types == NULL) {
                return NGX_CONF_ERROR;
            }

            type = ngx_array_push(conf->types);
            if (type == NULL) {
                return NGX_CONF_ERROR;
            }

            type->len = sizeof("text/html") - 1;
            type->data = (u_char *) "text/html";

        } else {
            conf->types = prev->types;
        }
    }

    return NGX_CONF_OK;
}


static ngx_int_t
ngx_http_ssi_filter_init(ngx_cycle_t *cycle)
{
    ngx_http_next_header_filter = ngx_http_top_header_filter;
    ngx_http_top_header_filter = ngx_http_ssi_header_filter;

    ngx_http_next_body_filter = ngx_http_top_body_filter;
    ngx_http_top_body_filter = ngx_http_ssi_body_filter;

    return NGX_OK;
}