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