nginx/src/http/modules/ngx_http_empty_gif_module.c

   1
   2 /*
   3  * Copyright (C) Igor Sysoev
   4  */
   5
   6 #include <ngx_config.h>
   7 #include <ngx_core.h>
   8 #include <ngx_http.h>
   9
  10
  11 static char *ngx_http_empty_gif(ngx_conf_t *cf, ngx_command_t *cmd,
  12     void *conf);
  13
  14 static ngx_command_t  ngx_http_empty_gif_commands[] = {
  15
  16     { ngx_string("empty_gif"),
  17       NGX_HTTP_LOC_CONF|NGX_CONF_NOARGS,
  18       ngx_http_empty_gif,
  19       0,
  20       0,
  21       NULL },
  22
  23       ngx_null_command
  24 };
  25
  26
  27 /* the minimal single pixel transparent GIF, 43 bytes */
  28
  29 static u_char  ngx_empty_gif[] = {
  30
  31     'G', 'I', 'F', '8', '9', 'a',  /* header                                 */
  32
  33                                    /* logical screen descriptor              */
  34     0x01, 0x00,                    /* logical screen width                   */
  35     0x01, 0x00,                    /* logical screen height                  */
  36     0x80,                          /* global 1-bit color table               */
  37     0x01,                          /* background color #1                    */
  38     0x00,                          /* no aspect ratio                        */
  39
  40                                    /* global color table                     */
  41     0x00, 0x00, 0x00,              /* #0: black                              */
  42     0xff, 0xff, 0xff,              /* #1: white                              */
  43
  44                                    /* graphic control extension              */
  45     0x21,                          /* extension introducer                   */
  46     0xf9,                          /* graphic control label                  */
  47     0x04,                          /* block size                             */
  48     0x01,                          /* transparent color is given,            */
  49                                    /*     no disposal specified,             */
  50                                    /*     user input is not expected         */
  51     0x00, 0x00,                    /* delay time                             */
  52     0x01,                          /* transparent color #1                   */
  53     0x00,                          /* block terminator                       */
  54
  55                                    /* image descriptor                       */
  56     0x2c,                          /* image separator                        */
  57     0x00, 0x00,                    /* image left position                    */
  58     0x00, 0x00,                    /* image top position                     */
  59     0x01, 0x00,                    /* image width                            */
  60     0x01, 0x00,                    /* image height                           */
  61     0x00,                          /* no local color table, no interlaced    */
  62
  63                                    /* table based image data                 */
  64     0x02,                          /* LZW minimum code size,                 */
  65                                    /*     must be at least 2-bit             */
  66     0x02,                          /* block size                             */
  67     0x4c, 0x01,                    /* compressed bytes 01_001_100, 0000000_1 */
  68                                    /* 100: clear code                        */
  69                                    /* 001: 1                                 */
  70                                    /* 101: end of information code           */
  71     0x00,                          /* block terminator                       */
  72
  73     0x3B                           /* trailer                                */
  74 };
  75
  76
  77 static ngx_http_module_t  ngx_http_empty_gif_module_ctx = {
  78     NULL,                          /* preconfiguration */
  79     NULL,                          /* postconfiguration */
  80
  81     NULL,                          /* create main configuration */
  82     NULL,                          /* init main configuration */
  83
  84     NULL,                          /* create server configuration */
  85     NULL,                          /* merge server configuration */
  86
  87     NULL,                          /* create location configuration */
  88     NULL                           /* merge location configuration */
  89 };
  90
  91
  92 ngx_module_t  ngx_http_empty_gif_module = {
  93     NGX_MODULE_V1,
  94     &ngx_http_empty_gif_module_ctx, /* module context */
  95     ngx_http_empty_gif_commands,   /* module directives */
  96     NGX_HTTP_MODULE,               /* module type */
  97     NULL,                          /* init master */
  98     NULL,                          /* init module */
  99     NULL,                          /* init process */
 100     NULL,                          /* init thread */
 101     NULL,                          /* exit thread */
 102     NULL,                          /* exit process */
 103     NULL,                          /* exit master */
 104     NGX_MODULE_V1_PADDING
 105 };
 106
 107
 108 static ngx_int_t
 109 ngx_http_empty_gif_handler(ngx_http_request_t *r)
 110 {
 111     ngx_int_t     rc;
 112     ngx_buf_t    *b;
 113     ngx_chain_t   out;
 114
 115     if (!(r->method & (NGX_HTTP_GET|NGX_HTTP_HEAD))) {
 116         return NGX_HTTP_NOT_ALLOWED;
 117     }
 118
 119     rc = ngx_http_discard_request_body(r);
 120
 121     if (rc != NGX_OK) {
 122         return rc;
 123     }
 124
 125     r->headers_out.content_type_len = sizeof("image/gif") - 1;
 126     r->headers_out.content_type.len = sizeof("image/gif") - 1;
 127     r->headers_out.content_type.data = (u_char *) "image/gif";
 128
 129     if (r->method == NGX_HTTP_HEAD) {
 130         r->headers_out.status = NGX_HTTP_OK;
 131         r->headers_out.content_length_n = sizeof(ngx_empty_gif);
 132         r->headers_out.last_modified_time = 23349600;
 133
 134         return ngx_http_send_header(r);
 135     }
 136
 137     b = ngx_pcalloc(r->pool, sizeof(ngx_buf_t));
 138     if (b == NULL) {
 139         return NGX_HTTP_INTERNAL_SERVER_ERROR;
 140     }
 141
 142     out.buf = b;
 143     out.next = NULL;
 144
 145     b->pos = ngx_empty_gif;
 146     b->last = ngx_empty_gif + sizeof(ngx_empty_gif);
 147     b->memory = 1;
 148     b->last_buf = 1;
 149
 150     r->headers_out.status = NGX_HTTP_OK;
 151     r->headers_out.content_length_n = sizeof(ngx_empty_gif);
 152     r->headers_out.last_modified_time = 23349600;
 153
 154     rc = ngx_http_send_header(r);
 155
 156     if (rc == NGX_ERROR || rc > NGX_OK || r->header_only) {
 157         return rc;
 158     }
 159
 160     return ngx_http_output_filter(r, &out);
 161 }
 162
 163
 164 static char *
 165 ngx_http_empty_gif(ngx_conf_t *cf, ngx_command_t *cmd, void *conf)
 166 {
 167     ngx_http_core_loc_conf_t  *clcf;
 168
 169     clcf = ngx_http_conf_get_module_loc_conf(cf, ngx_http_core_module);
 170     clcf->handler = ngx_http_empty_gif_handler;
 171
 172     return NGX_CONF_OK;
 173 }