mod_deflate.c

Apache HTTP Server 是一个功能强大的灵活的与HTTP/1.1相兼容的web服务器.这里给出的是Apache HTTP服务器的源码。

/* Copyright 2002-2005 The Apache Software Foundation or its licensors, as
 * applicable.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

/*
 * Portions of this software are based upon public domain software
 * (zlib functions gz_open and gzwrite)
 */

/*
 * mod_deflate.c: Perform deflate transfer-encoding on the fly
 *
 * Written by Ian Holsman
 *
 */

#include "httpd.h"
#include "http_config.h"
#include "http_log.h"
#include "apr_strings.h"
#include "apr_general.h"
#include "util_filter.h"
#include "apr_buckets.h"
#include "http_request.h"
#define APR_WANT_STRFUNC
#include "apr_want.h"

#include "zlib.h"

#ifdef HAVE_ZUTIL_H
#include "zutil.h"
#else
/* As part of the encoding process, we must send what our OS_CODE is
 * (or so it seems based on what I can tell of how gzip encoding works).
 *
 * zutil.h is not always included with zlib distributions (it is a private
 * header), so this is straight from zlib 1.1.3's zutil.h.
 */
#ifdef OS2
#define OS_CODE  0x06
#endif

#ifdef WIN32 /* Window 95 & Windows NT */
#define OS_CODE  0x0b
#endif

#if defined(VAXC) || defined(VMS)
#define OS_CODE  0x02
#endif

#ifdef AMIGA
#define OS_CODE  0x01
#endif

#if defined(ATARI) || defined(atarist)
#define OS_CODE  0x05
#endif

#if defined(MACOS) || defined(TARGET_OS_MAC)
#define OS_CODE  0x07
#endif

#ifdef __50SERIES /* Prime/PRIMOS */
#define OS_CODE  0x0F
#endif

#ifdef TOPS20
#define OS_CODE  0x0a
#endif

#ifndef OS_CODE
#define OS_CODE  0x03  /* assume Unix */
#endif
#endif

static const char deflateFilterName[] = "DEFLATE";
module AP_MODULE_DECLARE_DATA deflate_module;

typedef struct deflate_filter_config_t
{
    int windowSize;
    int memlevel;
    int compressionlevel;
    apr_size_t bufferSize;
    char *note_ratio_name;
    char *note_input_name;
    char *note_output_name;
} deflate_filter_config;

/* windowsize is negative to suppress Zlib header */
#define DEFAULT_COMPRESSION Z_DEFAULT_COMPRESSION
#define DEFAULT_WINDOWSIZE -15
#define DEFAULT_MEMLEVEL 9
#define DEFAULT_BUFFERSIZE 8096

/* Outputs a long in LSB order to the given file
 * only the bottom 4 bits are required for the deflate file format.
 */
static void putLong(unsigned char *string, unsigned long x)
{
    string[0] = (unsigned char)(x & 0xff);
    string[1] = (unsigned char)((x & 0xff00) >> 8);
    string[2] = (unsigned char)((x & 0xff0000) >> 16);
    string[3] = (unsigned char)((x & 0xff000000) >> 24);
}

/* Inputs a string and returns a long.
 */
static unsigned long getLong(unsigned char *string)
{
    return ((unsigned long)string[0])
          | (((unsigned long)string[1]) << 8)
          | (((unsigned long)string[2]) << 16)
          | (((unsigned long)string[3]) << 24);
}

static void *create_deflate_server_config(apr_pool_t *p, server_rec *s)
{
    deflate_filter_config *c = apr_pcalloc(p, sizeof *c);

    c->memlevel   = DEFAULT_MEMLEVEL;
    c->windowSize = DEFAULT_WINDOWSIZE;
    c->bufferSize = DEFAULT_BUFFERSIZE;
    c->compressionlevel = DEFAULT_COMPRESSION;

    return c;
}

static const char *deflate_set_window_size(cmd_parms *cmd, void *dummy,
                                           const char *arg)
{
    deflate_filter_config *c = ap_get_module_config(cmd->server->module_config,
                                                    &deflate_module);
    int i;

    i = atoi(arg);

    if (i < 1 || i > 15)
        return "DeflateWindowSize must be between 1 and 15";

    c->windowSize = i * -1;

    return NULL;
}

static const char *deflate_set_buffer_size(cmd_parms *cmd, void *dummy,
                                           const char *arg)
{
    deflate_filter_config *c = ap_get_module_config(cmd->server->module_config,
                                                    &deflate_module);
    int n = atoi(arg);

    if (n <= 0) {
        return "DeflateBufferSize should be positive";
    }

    c->bufferSize = (apr_size_t)n;

    return NULL;
}
static const char *deflate_set_note(cmd_parms *cmd, void *dummy,
                                    const char *arg1, const char *arg2)
{
    deflate_filter_config *c = ap_get_module_config(cmd->server->module_config,
                                                    &deflate_module);
    
    if (arg2 == NULL) {
        c->note_ratio_name = apr_pstrdup(cmd->pool, arg1);
    }
    else if (!strcasecmp(arg1, "ratio")) {
        c->note_ratio_name = apr_pstrdup(cmd->pool, arg2);
    }
    else if (!strcasecmp(arg1, "input")) {
        c->note_input_name = apr_pstrdup(cmd->pool, arg2);
    }
    else if (!strcasecmp(arg1, "output")) {
        c->note_output_name = apr_pstrdup(cmd->pool, arg2);
    }
    else {
        return apr_psprintf(cmd->pool, "Unknown note type %s", arg1);
    }

    return NULL;
}

static const char *deflate_set_memlevel(cmd_parms *cmd, void *dummy,
                                        const char *arg)
{
    deflate_filter_config *c = ap_get_module_config(cmd->server->module_config,
                                                    &deflate_module);
    int i;

    i = atoi(arg);

    if (i < 1 || i > 9)
        return "DeflateMemLevel must be between 1 and 9";

    c->memlevel = i;

    return NULL;
}

static const char *deflate_set_compressionlevel(cmd_parms *cmd, void *dummy,
                                        const char *arg)
{
    deflate_filter_config *c = ap_get_module_config(cmd->server->module_config,
                                                    &deflate_module);
    int i;

    i = atoi(arg);

    if (i < 1 || i > 9)
        return "Compression Level must be between 1 and 9";

    c->compressionlevel = i;

    return NULL;
}

/* magic header */
static char deflate_magic[2] = { '\037', '\213' };

typedef struct deflate_ctx_t
{
    z_stream stream;
    unsigned char *buffer;
    unsigned long crc;
    apr_bucket_brigade *bb, *proc_bb;
} deflate_ctx;

static apr_status_t deflate_out_filter(ap_filter_t *f,
                                       apr_bucket_brigade *bb)
{
    apr_bucket *e;
    request_rec *r = f->r;
    deflate_ctx *ctx = f->ctx;
    int zRC;
    deflate_filter_config *c = ap_get_module_config(r->server->module_config,
                                                    &deflate_module);

    /* If we don't have a context, we need to ensure that it is okay to send
     * the deflated content.  If we have a context, that means we've done
     * this before and we liked it.
     * This could be not so nice if we always fail.  But, if we succeed,
     * we're in better shape.
     */
    if (!ctx) {
        char *buf, *token;
        const char *encoding, *accepts;

        /* only work on main request/no subrequests */
        if (r->main) {
            ap_remove_output_filter(f);
            return ap_pass_brigade(f->next, bb);
        }

        /* some browsers might have problems, so set no-gzip
         * (with browsermatch) for them
         */
        if (apr_table_get(r->subprocess_env, "no-gzip")) {
            ap_remove_output_filter(f);
            return ap_pass_brigade(f->next, bb);
        }

        /* Some browsers might have problems with content types
         * other than text/html, so set gzip-only-text/html
         * (with browsermatch) for them
         */
        if (r->content_type == NULL
             || strncmp(r->content_type, "text/html", 9)) {
            const char *env_value = apr_table_get(r->subprocess_env,
                                                  "gzip-only-text/html");
            if ( env_value && (strcmp(env_value,"1") == 0) ) {
                ap_remove_output_filter(f);
                return ap_pass_brigade(f->next, bb);
            }            
        }

        /* Let's see what our current Content-Encoding is.
         * If it's already encoded, don't compress again.
         * (We could, but let's not.)
         */
        encoding = apr_table_get(r->headers_out, "Content-Encoding");
        if (encoding) {
            const char *err_enc;

            err_enc = apr_table_get(r->err_headers_out, "Content-Encoding");
            if (err_enc) {
                encoding = apr_pstrcat(r->pool, encoding, ",", err_enc, NULL);
            }
        }
        else {
            encoding = apr_table_get(r->err_headers_out, "Content-Encoding");
        }

        if (r->content_encoding) {
            encoding = encoding ? apr_pstrcat(r->pool, encoding, ",",
                                              r->content_encoding, NULL)
                                : r->content_encoding;
        }

        if (encoding) {
            const char *tmp = encoding;

            token = ap_get_token(r->pool, &tmp, 0);
            while (token && *token) {
                /* stolen from mod_negotiation: */
                if (strcmp(token, "identity") && strcmp(token, "7bit") &&
                    strcmp(token, "8bit") && strcmp(token, "binary")) {

                    ap_remove_output_filter(f);
                    return ap_pass_brigade(f->next, bb);			
                }

                /* Otherwise, skip token */
                if (*tmp) {
                    ++tmp;
                }
                token = (*tmp) ? ap_get_token(r->pool, &tmp, 0) : NULL;
            }
        }

        /* Even if we don't accept this request based on it not having
         * the Accept-Encoding, we need to note that we were looking
         * for this header and downstream proxies should be aware of that.
         */
        apr_table_setn(r->headers_out, "Vary", "Accept-Encoding");

        /* if they don't have the line, then they can't play */
        accepts = apr_table_get(r->headers_in, "Accept-Encoding");
        if (accepts == NULL) {
            ap_remove_output_filter(f);
            return ap_pass_brigade(f->next, bb);
        }

        token = ap_get_token(r->pool, &accepts, 0);
        while (token && token[0] && strcasecmp(token, "gzip")) {
            /* skip parameters, XXX: ;q=foo evaluation? */
            while (*accepts == ';') { 
                ++accepts;
                token = ap_get_token(r->pool, &accepts, 1);
            }

            /* retrieve next token */
            if (*accepts == ',') {
                ++accepts;
            }
            token = (*accepts) ? ap_get_token(r->pool, &accepts, 0) : NULL;
        }

        /* No acceptable token found. */
        if (token == NULL || token[0] == '\0') {
            ap_remove_output_filter(f);
            return ap_pass_brigade(f->next, bb);
        }

        /* We're cool with filtering this. */
        ctx = f->ctx = apr_pcalloc(r->pool, sizeof(*ctx));
        ctx->bb = apr_brigade_create(r->pool, f->c->bucket_alloc);
        ctx->buffer = apr_palloc(r->pool, c->bufferSize);

        zRC = deflateInit2(&ctx->stream, c->compressionlevel, Z_DEFLATED,
                           c->windowSize, c->memlevel,
                           Z_DEFAULT_STRATEGY);

        if (zRC != Z_OK) {
            f->ctx = NULL;
            ap_log_rerror(APLOG_MARK, APLOG_ERR, 0, r,
                          "unable to init Zlib: "
                          "deflateInit2 returned %d: URL %s",
                          zRC, r->uri);
            return ap_pass_brigade(f->next, bb);
        }

        /* RFC 1952 Section 2.3 dictates the gzip header:
         *
         * +---+---+---+---+---+---+---+---+---+---+
         * |ID1|ID2|CM |FLG|     MTIME     |XFL|OS |
         * +---+---+---+---+---+---+---+---+---+---+
         *
         * If we wish to populate in MTIME (as hinted in RFC 1952), do:
         * putLong(date_array, apr_time_now() / APR_USEC_PER_SEC);
         * where date_array is a char[4] and then print date_array in the
         * MTIME position.  WARNING: ENDIANNESS ISSUE HERE.
         */
        buf = apr_psprintf(r->pool, "%c%c%c%c%c%c%c%c%c%c", deflate_magic[0],
                           deflate_magic[1], Z_DEFLATED, 0 /* flags */,
                           0, 0, 0, 0 /* 4 chars for mtime */,
                           0 /* xflags */, OS_CODE);
        e = apr_bucket_pool_create(buf, 10, r->pool, f->c->bucket_alloc);
        APR_BRIGADE_INSERT_TAIL(ctx->bb, e);

        /* If the entire Content-Encoding is "identity", we can replace it. */
        if (!encoding || !strcasecmp(encoding, "identity")) {
            apr_table_setn(r->headers_out, "Content-Encoding", "gzip");
        }
        else {
            apr_table_mergen(r->headers_out, "Content-Encoding", "gzip");
        }
        apr_table_unset(r->headers_out, "Content-Length");

        /* initialize deflate output buffer */
        ctx->stream.next_out = ctx->buffer;
        ctx->stream.avail_out = c->bufferSize;
    }
    
    while (!APR_BRIGADE_EMPTY(bb))
    {
        const char *data;
        apr_bucket *b;
        apr_size_t len;
        int done = 0;

        e = APR_BRIGADE_FIRST(bb);

        if (APR_BUCKET_IS_EOS(e)) {
            char *buf;
            unsigned int deflate_len;

            ctx->stream.avail_in = 0; /* should be zero already anyway */
            for (;;) {
                deflate_len = c->bufferSize - ctx->stream.avail_out;

                if (deflate_len != 0) {
                    b = apr_bucket_heap_create((char *)ctx->buffer,
                                               deflate_len, NULL,