通过对nginx服务器的工作进程进行调试，可以发现在请求html页面时，在调用http模块过程中堆栈记录的信息如下：
(gdb) BT
#0 ngx_http_read_request_header (r=0x1bf3fc0) at src/http/ngx_http_request.c:1374
#1 0x0000000000447bc9 in ngx_http_process_request_line (rev=0x1c0a2f0) at src/http/ngx_http_request.c:940
#2 0x00000000004476c1 in ngx_http_wait_request_handler (rev=0x1c0a2f0) at src/http/ngx_http_request.c:499
#3 0x0000000000436f30 in ngx_epoll_process_events (cycle=0x1be8f50, timer=60000, flags=1)
at src/event/modules/ngx_epoll_module.c:822
#4 0x000000000042a3d2 in ngx_process_events_and_timers (cycle=0x1be8f50) at src/event/ngx_event.c:242
#5 0x0000000000434faf in ngx_worker_process_cycle (cycle=0x1be8f50, data=0x0) at src/os/unix/ngx_process_cycle.c:753
#6 0x0000000000431f57 in ngx_spawn_process (cycle=0x1be8f50, proc=0x434ef0 <ngx_worker_process_cycle>, data=0x0,
name=0x4b0f10 "worker process", respawn=-3) at src/os/unix/ngx_process.c:198
#7 0x00000000004341e3 in ngx_start_worker_processes (cycle=0x1be8f50, n=1, type=-3) at src/os/unix/ngx_process_cycle.c:358
#8 0x0000000000433966 in ngx_master_process_cycle (cycle=0x1be8f50) at src/os/unix/ngx_process_cycle.c:130
#9 0x0000000000403cb7 in main (argc=1, argv=0x7fff63b94e98) at src/core/nginx.c:359
可以查看出读取到的数据，是浏览器发出的html请求的报头
(gdb) p b->last
$59 = (
unsigned char *) 0x1bf3b60 "GET / HTTP/1.1\r\nHost: 192.168.1.103\r\nConnection: keep-alive\r\nCache-Control: max-age=0\r\nAccept
: text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,*/*;q=0.8\r\nUpgrade-Insecure-Requests: 1\r"...
以下是在处理GET请求中的流程
(gdb) bt
#0 ngx_http_parse_request_line (r=0x256afc0, b=0x256a850) at src/http/ngx_http_parse.c:146
#1 0x0000000000447bfa in ngx_http_process_request_line (rev=0x25812f0) at src/http/ngx_http_request.c:947
#2 0x00000000004476c1 in ngx_http_wait_request_handler (rev=0x25812f0) at src/http/ngx_http_request.c:499
#3 0x0000000000436f30 in ngx_epoll_process_events (cycle=0x255ff50, timer=60000, flags=1)
at src/event/modules/ngx_epoll_module.c:822
#4 0x000000000042a3d2 in ngx_process_events_and_timers (cycle=0x255ff50) at src/event/ngx_event.c:242
#5 0x0000000000434faf in ngx_worker_process_cycle (cycle=0x255ff50, data=0x0) at src/os/unix/ngx_process_cycle.c:753
#6 0x0000000000431f57 in ngx_spawn_process (cycle=0x255ff50, proc=0x434ef0 <ngx_worker_process_cycle>, data=0x0,
name=0x4b0f10 "worker process", respawn=-3) at src/os/unix/ngx_process.c:198
#7 0x00000000004341e3 in ngx_start_worker_processes (cycle=0x255ff50, n=1, type=-3) at src/os/unix/ngx_process_cycle.c:358
#8 0x0000000000433966 in ngx_master_process_cycle (cycle=0x255ff50) at src/os/unix/ngx_process_cycle.c:130
#9 0x0000000000403cb7 in main (argc=1, argv=0x7fff62ed08a8) at src/core/nginx.c:359
对照代码，可以看出是在处理http协议的头部
通过debug以及review该处代码，可以看出，针对 头部协议，该处逻辑采用了状态器模式，在逻辑处理中，根据不同的逻辑，设置不同的ch状态属性，然后根据不同的状态属性，进入大不同的处理逻辑之中。这样的处理模式非常通用，在服务器开发中，应用状态器模式，在不同的心跳进行不同的处理。
ngx_int_t
ngx_http_parse_request_line(ngx_http_request_t *r, ngx_buf_t *b)
{
u_char c, ch, *p, *m;
enum {
sw_start = 0,
sw_method,
sw_spaces_before_uri,
sw_schema,
sw_schema_slash,
sw_schema_slash_slash,
sw_host_start,
sw_host,
sw_host_end,
sw_host_ip_literal,
sw_port,
sw_host_http_09,
sw_after_slash_in_uri,
sw_check_uri,
sw_check_uri_http_09,
sw_uri,
sw_http_09,
sw_http_H,
sw_http_HT,
sw_http_HTT,
sw_http_HTTP,
sw_first_major_digit,
sw_major_digit,
sw_first_minor_digit,
sw_minor_digit,
sw_spaces_after_digit,
sw_almost_done
} state;
state = r->state;
for (p = b->pos; p < b->last; p++) {
ch = *p;
switch (state) {
/* HTTP methods: GET, HEAD, POST */
case sw_start:
r->request_start = p;
if (ch == CR || ch == LF) {
break;
}
if ((ch < 'A' || ch > 'Z') && ch != '_') {
return NGX_HTTP_PARSE_INVALID_METHOD;
}
state = sw_method;
break;
case sw_method:
if (ch == ' ') {
r->method_end = p - 1;
m = r->request_start;
switch (p - m) {
case 3:
if (ngx_str3_cmp(m, 'G', 'E', 'T', ' ')) {
r->method = NGX_HTTP_GET;
break;
}
if (ngx_str3_cmp(m, 'P', 'U', 'T', ' ')) {
r->method = NGX_HTTP_PUT;
break;
}
break;
case 4:
if (m[1] == 'O') {
if (ngx_str3Ocmp(m, 'P', 'O', 'S', 'T')) {
r->method = NGX_HTTP_POST;
break;
}
if (ngx_str3Ocmp(m, 'C', 'O', 'P', 'Y')) {
r->method = NGX_HTTP_COPY;
break;
}
if (ngx_str3Ocmp(m, 'M', 'O', 'V', 'E')) {
r->method = NGX_HTTP_MOVE;
break;
}
if (ngx_str3Ocmp(m, 'L', 'O', 'C', 'K')) {
r->method = NGX_HTTP_LOCK;
break;
}
} else {
if (ngx_str4cmp(m, 'H', 'E', 'A', 'D')) {
r->method = NGX_HTTP_HEAD;
break;
}
}
break;
case 5:
if (ngx_str5cmp(m, 'M', 'K', 'C', 'O', 'L')) {
r->method = NGX_HTTP_MKCOL;
break;
}
if (ngx_str5cmp(m, 'P', 'A', 'T', 'C', 'H')) {
r->method = NGX_HTTP_PATCH;
break;
}
if (ngx_str5cmp(m, 'T', 'R', 'A', 'C', 'E')) {
r->method = NGX_HTTP_TRACE;
break;
}
break;
case 6:
if (ngx_str6cmp(m, 'D', 'E', 'L', 'E', 'T', 'E')) {
r->method = NGX_HTTP_DELETE;
break;
}
if (ngx_str6cmp(m, 'U', 'N', 'L', 'O', 'C', 'K')) {
r->method = NGX_HTTP_UNLOCK;
break;
}
break;
case 7:
if (ngx_str7_cmp(m, 'O', 'P', 'T', 'I', 'O', 'N', 'S', ' '))
{
r->method = NGX_HTTP_OPTIONS;
}
break;
case 8:
if (ngx_str8cmp(m, 'P', 'R', 'O', 'P', 'F', 'I', 'N', 'D'))
{
r->method = NGX_HTTP_PROPFIND;
}
break;
case 9:
if (ngx_str9cmp(m,
'P', 'R', 'O', 'P', 'P', 'A', 'T', 'C', 'H'))
{
r->method = NGX_HTTP_PROPPATCH;
}
break;
}
state = sw_spaces_before_uri;
break;
}
if ((ch < 'A' || ch > 'Z') && ch != '_') {
return NGX_HTTP_PARSE_INVALID_METHOD;
}
break;
/* space* before URI */
case sw_spaces_before_uri:
if (ch == '/') {
r->uri_start = p;
state = sw_after_slash_in_uri;
break;
}
c = (u_char) (ch | 0x20);
if (c >= 'a' && c <= 'z') {
r->schema_start = p;
state = sw_schema;
break;
}
switch (ch) {
case ' ':
break;
default:
return NGX_HTTP_PARSE_INVALID_REQUEST;
}
break;
case sw_schema:
c = (u_char) (ch | 0x20);
if (c >= 'a' && c <= 'z') {
break;
}
switch (ch) {
case ':':
r->schema_end = p;
state = sw_schema_slash;
break;
default:
return NGX_HTTP_PARSE_INVALID_REQUEST;
}
break;
case sw_schema_slash:
switch (ch) {
case '/':
state = sw_schema_slash_slash;
break;
default:
return NGX_HTTP_PARSE_INVALID_REQUEST;
}
break;
case sw_schema_slash_slash:
switch (ch) {
case '/':
state = sw_host_start;
break;
default:
return NGX_HTTP_PARSE_INVALID_REQUEST;
}
break;
case sw_host_start:
r->host_start = p;
if (ch == '[') {
state = sw_host_ip_literal;
break;
}
state = sw_host;
/* fall through */
case sw_host:
c = (u_char) (ch | 0x20);
if (c >= 'a' && c <= 'z') {
break;
}
if ((ch >= '0' && ch <= '9') || ch == '.' || ch == '-') {
break;
}
/* fall through */
case sw_host_end:
r->host_end = p;
switch (ch) {
case ':':
state = sw_port;
break;
case '/':
r->uri_start = p;
state = sw_after_slash_in_uri;
break;
case ' ':
/*
* use single "/" from request line to preserve pointers,
* if request line will be copied to large client buffer
*/
r->uri_start = r->schema_end + 1;
r->uri_end = r->schema_end + 2;
state = sw_host_http_09;
break;
default:
return NGX_HTTP_PARSE_INVALID_REQUEST;
}
break;
case sw_host_ip_literal:
if (ch >= '0' && ch <= '9') {
break;
}
c = (u_char) (ch | 0x20);
if (c >= 'a' && c <= 'z') {
break;
}
switch (ch) {
case ':':
break;
case ']':
state = sw_host_end;
break;
case '-':
case '.':
case '_':
case '~':
/* unreserved */
break;
case '!':
case '$':
case '&':
case '\'':
case '(':
case ')':
case '*':
case '+':
case ',':
case ';':
case '=':
/* sub-delims */
break;
default:
return NGX_HTTP_PARSE_INVALID_REQUEST;
}
break;
case sw_port:
if (ch >= '0' && ch <= '9') {
break;
}
switch (ch) {
case '/':
r->port_end = p;
r->uri_start = p;
state = sw_after_slash_in_uri;
break;
case ' ':
r->port_end = p;
/*
* use single "/" from request line to preserve pointers,
* if request line will be copied to large client buffer
*/
r->uri_start = r->schema_end + 1;
r->uri_end = r->schema_end + 2;
state = sw_host_http_09;
break;
default:
return NGX_HTTP_PARSE_INVALID_REQUEST;
}
break;
/* space+ after "http://host[:port] " */
case sw_host_http_09:
switch (ch) {
case ' ':
break;
case CR:
r->http_minor = 9;
state = sw_almost_done;
break;
case LF:
r->http_minor = 9;
goto done;
case 'H':
r->http_protocol.data = p;
state = sw_http_H;
break;
default:
return NGX_HTTP_PARSE_INVALID_REQUEST;
}
break;
/* check "/.", "//", "%", and "\" (Win32) in URI */
case sw_after_slash_in_uri:
if (usual[ch >> 5] & (1 << (ch & 0x1f))) {
state = sw_check_uri;
break;
}
switch (ch) {
case ' ':
r->uri_end = p;
state = sw_check_uri_http_09;
break;
case CR:
r->uri_end = p;
r->http_minor = 9;
state = sw_almost_done;
break;
case LF:
r->uri_end = p;
r->http_minor = 9;
goto done;
case '.':
r->complex_uri = 1;
state = sw_uri;
break;
case '%':
r->quoted_uri = 1;
state = sw_uri;
break;
case '/':
r->complex_uri = 1;
state = sw_uri;
break;
#if (NGX_WIN32)
case '\\':
r->complex_uri = 1;
state = sw_uri;
break;
#endif
case '?':
r->args_start = p + 1;
state = sw_uri;
break;
case '#':
r->complex_uri = 1;
state = sw_uri;
break;
case '+':
r->plus_in_uri = 1;
break;
case '\0':
return NGX_HTTP_PARSE_INVALID_REQUEST;
default:
state = sw_check_uri;
break;
}
break;
/* check "/", "%" and "\" (Win32) in URI */
case sw_check_uri:
if (usual[ch >> 5] & (1 << (ch & 0x1f))) {
break;
}
switch (ch) {
case '/':
#if (NGX_WIN32)
if (r->uri_ext == p) {
r->complex_uri = 1;
state = sw_uri;
break;
}
#endif
r->uri_ext = NULL;
state = sw_after_slash_in_uri;
break;
case '.':
r->uri_ext = p + 1;
break;
case ' ':
r->uri_end = p;
state = sw_check_uri_http_09;
break;
case CR:
r->uri_end = p;
r->http_minor = 9;
state = sw_almost_done;
break;
case LF:
r->uri_end = p;
r->http_minor = 9;
goto done;
#if (NGX_WIN32)
case '\\':
r->complex_uri = 1;
state = sw_after_slash_in_uri;
break;
#endif
case '%':
r->quoted_uri = 1;
state = sw_uri;
break;
case '?':
r->args_start = p + 1;
state = sw_uri;
break;
case '#':
r->complex_uri = 1;
state = sw_uri;
break;
case '+':
r->plus_in_uri = 1;
break;
case '\0':
return NGX_HTTP_PARSE_INVALID_REQUEST;
}
break;
/* space+ after URI */
case sw_check_uri_http_09:
switch (ch) {
case ' ':
break;
case CR:
r->http_minor = 9;
state = sw_almost_done;
break;
case LF:
r->http_minor = 9;
goto done;
case 'H':
r->http_protocol.data = p;
state = sw_http_H;
break;
default:
r->space_in_uri = 1;
state = sw_check_uri;
p--;
break;
}
break;
/* URI */
case sw_uri:
if (usual[ch >> 5] & (1 << (ch & 0x1f))) {
break;
}
switch (ch) {
case ' ':
r->uri_end = p;
state = sw_http_09;
break;
case CR:
r->uri_end = p;
r->http_minor = 9;
state = sw_almost_done;
break;
case LF:
r->uri_end = p;
r->http_minor = 9;
goto done;
case '#':
r->complex_uri = 1;
break;
case '\0':
return NGX_HTTP_PARSE_INVALID_REQUEST;
}
break;
/* space+ after URI */
case sw_http_09:
switch (ch) {
case ' ':
break;
case CR:
r->http_minor = 9;
state = sw_almost_done;
break;
case LF:
r->http_minor = 9;
goto done;
case 'H':
r->http_protocol.data = p;
state = sw_http_H;
break;
default:
r->space_in_uri = 1;
state = sw_uri;
p--;
break;
}
break;
case sw_http_H:
switch (ch) {
case 'T':
state = sw_http_HT;
break;
default:
return NGX_HTTP_PARSE_INVALID_REQUEST;
}
break;
case sw_http_HT:
switch (ch) {
case 'T':
state = sw_http_HTT;
break;
default:
return NGX_HTTP_PARSE_INVALID_REQUEST;
}
break;
case sw_http_HTT:
switch (ch) {
case 'P':
state = sw_http_HTTP;
break;
default:
return NGX_HTTP_PARSE_INVALID_REQUEST;
}
break;
case sw_http_HTTP:
switch (ch) {
case '/':
state = sw_first_major_digit;
break;
default:
return NGX_HTTP_PARSE_INVALID_REQUEST;
}
break;
/* first digit of major HTTP version */
case sw_first_major_digit:
if (ch < '1' || ch > '9') {
return NGX_HTTP_PARSE_INVALID_REQUEST;
}
r->http_major = ch - '0';
state = sw_major_digit;
break;
/* major HTTP version or dot */
case sw_major_digit:
if (ch == '.') {
state = sw_first_minor_digit;
break;
}
if (ch < '0' || ch > '9') {
return NGX_HTTP_PARSE_INVALID_REQUEST;
}
r->http_major = r->http_major * 10 + ch - '0';
break;
/* first digit of minor HTTP version */
case sw_first_minor_digit:
if (ch < '0' || ch > '9') {
return NGX_HTTP_PARSE_INVALID_REQUEST;
}
r->http_minor = ch - '0';
state = sw_minor_digit;
break;
/* minor HTTP version or end of request line */
case sw_minor_digit:
if (ch == CR) {
state = sw_almost_done;
break;
}
if (ch == LF) {
goto done;
}
if (ch == ' ') {
state = sw_spaces_after_digit;
break;
}
if (ch < '0' || ch > '9') {
return NGX_HTTP_PARSE_INVALID_REQUEST;
}
r->http_minor = r->http_minor * 10 + ch - '0';
break;
case sw_spaces_after_digit:
switch (ch) {
case ' ':
break;
case CR:
state = sw_almost_done;
break;
case LF:
goto done;
default:
return NGX_HTTP_PARSE_INVALID_REQUEST;
}
break;
/* end of request line */
case sw_almost_done:
r->request_end = p - 1;
switch (ch) {
case LF:
goto done;
default:
return NGX_HTTP_PARSE_INVALID_REQUEST;
}
}
}
b->pos = p;
r->state = state;
return NGX_AGAIN;
done:
b->pos = p + 1;
if (r->request_end == NULL) {
r->request_end = p;
}
r->http_version = r->http_major * 1000 + r->http_minor;
r->state = sw_start;
if (r->http_version == 9 && r->method != NGX_HTTP_GET) {
return NGX_HTTP_PARSE_INVALID_09_METHOD;
}
return NGX_OK;
}
