Anatomy Nginx Module Development (3) Basic function Realization of Ngx_http_hello_world_module module

Remember when we defined a struct as follows?

typedef struct {    ngx_str_t output_words;} ngx_http_hello_world_loc_conf_t;

It is the location component configuration of HelloWorld, which has a string member Output_words.

1 Create Location

Used for location creation functions in Ngx_http_hello_world_module_ctx:

static void* ngx_http_hello_world_create_loc_conf(ngx_conf_t* cf) {    ngx_http_hello_world_loc_conf_t* conf;    conf = ngx_pcalloc(cf->pool, sizeof(ngx_http_hello_world_loc_conf_t));    if (conf == NULL) {        return NGX_CONF_ERROR;    }    conf->output_words.len = 0;    conf->output_words.data = NULL;    return conf;}

As we can see, we are allocating the memory of the size of the ngx_http_hello_world_loc_conf_t used first. And initializes the ngx_http_hello_world_loc_conf_t unique member Output_words.

2 Merge Location

For the location merge function in Ngx_http_hello_world_module_ctx:

static char* ngx_http_hello_world_merge_loc_conf(ngx_conf_t* cf,        void* parent,        void* child) {    ngx_http_hello_world_loc_conf_t* prev = parent;    ngx_http_hello_world_loc_conf_t* conf = child;    ngx_conf_merge_str_value(conf->output_words, prev->output_words, "boy");    return NGX_CONF_OK;}

3 ngx_http_hello_world3.1 ngx_http_conf_get_module_loc_conf

First you need to understand a "function" provided by Nginx:

ngx_http_conf_get_module_loc_conf(    cf, // configuration    module);

In fact, it is a macro definition, in Ngx_http_config.h:

#define ngx_http_conf_get_module_loc_conf(cf, module)     ((ngx_http_conf_ctx_t *) cf->ctx)->loc_conf[module.ctx_index]

Its role is to locate the location configuration in the specified module by using the context of the CF configuration.

3.2 Ngx_http_hello_world

The set field for the only command we define in Ngx_http_hello_world_commands.

 static char* Ngx_http_hello_world (ngx_conf_t* CF, ngx_command_t* cmd, void* conf) {Ngx_http_core_loc_co    nf_t* CLCF;    CLCF = ngx_http_conf_get_module_loc_conf (cf, Ngx_http_core_module);    Clcf->handler = Ngx_http_hello_world_handler;    Ngx_conf_set_str_slot (cf, CMD, conf); return NGX_CONF_OK;}  

The function is to generate a response to the request, that is, in this case hello_world, Poechant . Then get to the location configuration of Http_core_module, CLCF (core location ConF). Assign a value Ngx_http_hello_world_handler to the handler field of CLCF, which is described below. The Ngx_conf_set_str_slot is then routinely called.

4 Ngx_http_hello_world_handler

First you need to know a "function" provided by Nginx:

4.1 ngx_http_conf_get_module_loc_conf

ngx_http_conf_get_module_loc_conf(    r, // request    module);

In fact, it is a macro definition, in Ngx_http_config.h:

#define ngx_http_get_module_loc_conf(r, module)  (r)->loc_conf[module.ctx_index]

The function is to find the location configuration requested by the request according to the module's index field (Ctx_index).

4.2 Ngx_http_hello_world_handler

First of all, look at the more classic Nginx buffer ngx_buf_t bar. Only the sections related to this article are described here.

struct ngx_buf_s {    u_char          *pos;    u_char          *last;    u_char          *start;         /* start of buffer */    u_char          *end;           /* end of buffer */    …};

These four pointers divide the buffer into 3 parts. The following are the differences:

• • read-only buffers: for read-only buffers, this is part of the read-only section;
• Part Two (Pos to last): Blockquote style= "BORDER-LEFT-WIDTH:4PX; Border-left-style:solid; Border-left-color: #dddddd; Color: #444444; padding-top:0px; padding-right:15px; padding-bottom:0px; padding-left:15px; margin:0px; " >
  • read-only buffers: for read-only buffers, this is part of the read-only section;
  • write buffers only: For write-only buffers, the area that has been written.
• The third part (last to end):

  • Read-only buffers: there is no such part for read-only buffers;
  • Write-only buffers: for write-only buffers, the remaining writable regions.

Another reason why ngx_buf_t Classic is because nginx can flush the output in advance, so these buf can be reused after output, can avoid redistribution, improve system performance, known as FREE_BUF, and not be output buf is busy_buf.

So come and see Ngx_http_hello_world_handler:

Static ngx_int_t Ngx_http_hello_world_handler (ngx_http_request_t* r) {ngx_int_t rc;    ngx_buf_t* b;    Ngx_chain_t out[2];    ngx_http_hello_world_loc_conf_t* HLCF;    HLCF = ngx_http_get_module_loc_conf (R, Ngx_http_hello_world_module);    Set the header of the request R->headers_out.content_type.len = sizeof ("Text/plain")-1;    R->headers_out.content_type.data = (u_char*) "Text/plain";    Allocate buffer memory Space B = Ngx_pcalloc (R->pool, sizeof (ngx_buf_t));    1th block buffer out[0].buf = b;    Out[0].next = &out[1];    In this module, buffers only need to write data, so only set pos and last B->pos = (u_char*) "Hello_world,";    B->last = b->pos + sizeof ("Hello_world,")-1; B->memory = 1;    The indicator buffer is memory buffer//allocation buffer for memory space B = Ngx_pcalloc (R->pool, sizeof (ngx_buf_t));    2nd block Buffer out[1].buf = b;    Out[1].next = NULL;    In this module, buffers only need to write data, so only pos and last B->pos = hlcf->output_words.data; are set    B->last = Hlcf->output_words.data + (Hlcf->output_words.len); B->memory = 1; The indicator buffer is memory buffered B->LAST_BUF = 1;    Mark the entire response to the last buffer, Nginx will immediately send buffer all the data//Set the header of the request R->headers_out.status = NGX_HTTP_OK;    R->headers_out.content_length_n = Hlcf->output_words.len + sizeof ("Hello_world,")-1;    Send Request rc = Ngx_http_send_header (r);    if (rc = = Ngx_error | | rc > NGX_OK | | r->header_only) {return rc; } return Ngx_http_output_filter (R, &out[0]);}

5 Reference

1. Www.evanmiller.org/nginx-modules-guide.html
2. Http://blog.sina.com.cn/s/blog_7303a1dc0100x70t.html

-

Anatomy Nginx Module Development (3) Basic function Realization of Ngx_http_hello_world_module module