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