core/ngx_file.c源文件分析(1)
本节我们讲述一下nginx中对所涉及到的文件操作。
1. 相关变量定义
/*
* Copyright (C) Igor Sysoev
* Copyright (C) Nginx, Inc.
*/
#include <ngx_config.h>
#include <ngx_core.h>
static ngx_int_t ngx_test_full_name(ngx_str_t *name);
static ngx_atomic_t temp_number = 0;
ngx_atomic_t *ngx_temp_number = &temp_number;
ngx_atomic_int_t ngx_random_number = 123456;-
函数
ngx_test_full_name()用于判断name是否为一个绝对路径。 -
变量
temp_number作为一个临时的占位符空间 -
变量
ngx_temp_number刚开始指向temp_number,而后在初始化event模块时（ngx_event_module_init()函数)，指向一个共享内存空间，在整个Nginx中作为一个临时值使用 -
变量ngx_random_number作为随机值使用，默认初始化值为123456，而在event模块初始化时，被设置为：
ngx_random_number = (tp->msec << 16) + ngx_pid;2. 函数ngx_get_full_name()
ngx_int_t
ngx_get_full_name(ngx_pool_t *pool, ngx_str_t *prefix, ngx_str_t *name)
{
size_t len;
u_char *p, *n;
ngx_int_t rc;
rc = ngx_test_full_name(name);
if (rc == NGX_OK) {
return rc;
}
len = prefix->len;
#if (NGX_WIN32)
if (rc == 2) {
len = rc;
}
#endif
n = ngx_pnalloc(pool, len + name->len + 1);
if (n == NULL) {
return NGX_ERROR;
}
p = ngx_cpymem(n, prefix->data, len);
ngx_cpystrn(p, name->data, name->len + 1);
name->len += len;
name->data = n;
return NGX_OK;
}这里先判断name是否是一个绝对路径，如果是则直接返回OK；否则开辟一块空间，将name追加到prefix后（注意，这里会以’\0’结尾)
3. 函数ngx_test_full_name()
static ngx_int_t
ngx_test_full_name(ngx_str_t *name)
{
#if (NGX_WIN32)
u_char c0, c1;
c0 = name->data[0];
if (name->len < 2) {
if (c0 == '/') {
return 2;
}
return NGX_DECLINED;
}
c1 = name->data[1];
if (c1 == ':') {
c0 |= 0x20;
if ((c0 >= 'a' && c0 <= 'z')) {
return NGX_OK;
}
return NGX_DECLINED;
}
if (c1 == '/') {
return NGX_OK;
}
if (c0 == '/') {
return 2;
}
return NGX_DECLINED;
#else
if (name->data[0] == '/') {
return NGX_OK;
}
return NGX_DECLINED;
#endif
}在WIN32上判断是否是一个绝对路径，例如C:，又或者是以类似于<charactor>/这样开头的路径； 对于在其他操作系统环境上则直接判断是否为绝对路径。在当前环境下，我们并不支持NGX_WIN32宏定义。
4. 函数ngx_write_chain_to_temp_file()
ssize_t
ngx_write_chain_to_temp_file(ngx_temp_file_t *tf, ngx_chain_t *chain)
{
ngx_int_t rc;
if (tf->file.fd == NGX_INVALID_FILE) {
rc = ngx_create_temp_file(&tf->file, tf->path, tf->pool,
tf->persistent, tf->clean, tf->access);
if (rc != NGX_OK) {
return rc;
}
if (tf->log_level) {
ngx_log_error(tf->log_level, tf->file.log, 0, "%s %V",
tf->warn, &tf->file.name);
}
}
#if (NGX_THREADS && NGX_HAVE_PWRITEV)
if (tf->thread_write) {
return ngx_thread_write_chain_to_file(&tf->file, chain, tf->offset,
tf->pool);
}
#endif
return ngx_write_chain_to_file(&tf->file, chain, tf->offset, tf->pool);
}这里首先判断tf->file.fd是否为一个有效的文件句柄，如果不是则先创建一个临时文件。接着将chain中的数据写入到tf临时文件中。
5. 函数ngx_create_temp_file()
ngx_int_t
ngx_create_temp_file(ngx_file_t *file, ngx_path_t *path, ngx_pool_t *pool,
ngx_uint_t persistent, ngx_uint_t clean, ngx_uint_t access)
{
uint32_t n;
ngx_err_t err;
ngx_pool_cleanup_t *cln;
ngx_pool_cleanup_file_t *clnf;
file->name.len = path->name.len + 1 + path->len + 10;
file->name.data = ngx_pnalloc(pool, file->name.len + 1);
if (file->name.data == NULL) {
return NGX_ERROR;
}
#if 0
for (i = 0; i < file->name.len; i++) {
file->name.data[i] = 'X';
}
#endif
ngx_memcpy(file->name.data, path->name.data, path->name.len);
n = (uint32_t) ngx_next_temp_number(0);
cln = ngx_pool_cleanup_add(pool, sizeof(ngx_pool_cleanup_file_t));
if (cln == NULL) {
return NGX_ERROR;
}
for ( ;; ) {
(void) ngx_sprintf(file->name.data + path->name.len + 1 + path->len,
"%010uD%Z", n);
ngx_create_hashed_filename(path, file->name.data, file->name.len);
ngx_log_debug1(NGX_LOG_DEBUG_CORE, file->log, 0,
"hashed path: %s", file->name.data);
file->fd = ngx_open_tempfile(file->name.data, persistent, access);
ngx_log_debug1(NGX_LOG_DEBUG_CORE, file->log, 0,
"temp fd:%d", file->fd);
if (file->fd != NGX_INVALID_FILE) {
cln->handler = clean ? ngx_pool_delete_file : ngx_pool_cleanup_file;
clnf = cln->data;
clnf->fd = file->fd;
clnf->name = file->name.data;
clnf->log = pool->log;
return NGX_OK;
}
err = ngx_errno;
if (err == NGX_EEXIST_FILE) {
n = (uint32_t) ngx_next_temp_number(1);
continue;
}
if ((path->level[0] == 0) || (err != NGX_ENOPATH)) {
ngx_log_error(NGX_LOG_CRIT, file->log, err,
ngx_open_tempfile_n " \"%s\" failed",
file->name.data);
return NGX_ERROR;
}
if (ngx_create_path(file, path) == NGX_ERROR) {
return NGX_ERROR;
}
}
}本函数用于创建一个临时文件，具体创建步骤如下：
- 为file->name分配空间，空间大小为：
file->name.len = path->name.len + 1 + path->len + 10;
这里path->len为文件的多级目录结构长度，之所以要再加10，是因为创建临时文件会加一个随机值到文件名后（uint32_t所表示的数最大长度为10个字节)
-
接着创建一个ngx_pool_cleanup_t数据结构，以再后续对临时文件清除时调用
-
产生临时文件名，并创建临时文件
(void) ngx_sprintf(file->name.data + path->name.len + 1 + path->len,
"%010uD%Z", n);
ngx_create_hashed_filename(path, file->name.data, file->name.len);
ngx_log_debug1(NGX_LOG_DEBUG_CORE, file->log, 0,
"hashed path: %s", file->name.data);
file->fd = ngx_open_tempfile(file->name.data, persistent, access);这里首先将产生的整数n格式化为宽度为10的字符串，以'\0'结尾，到目前为止,file->name为如下：
然后创建hash文件名，最后再创建临时文件。
6. 函数ngx_create_hashed_filename()
void
ngx_create_hashed_filename(ngx_path_t *path, u_char *file, size_t len)
{
size_t i, level;
ngx_uint_t n;
i = path->name.len + 1;
file[path->name.len + path->len] = '/';
for (n = 0; n < 3; n++) {
level = path->level[n];
if (level == 0) {
break;
}
len -= level;
file[i - 1] = '/';
ngx_memcpy(&file[i], &file[len], level);
i += level + 1;
}
}这里首先在path->name.len+path->len为止处添加’/’字符，然后分别产生每一级的Hash路径。
7. 函数ngx_create_path()
ngx_int_t
ngx_create_path(ngx_file_t *file, ngx_path_t *path)
{
size_t pos;
ngx_err_t err;
ngx_uint_t i;
pos = path->name.len;
for (i = 0; i < 3; i++) {
if (path->level[i] == 0) {
break;
}
pos += path->level[i] + 1;
file->name.data[pos] = '\0';
ngx_log_debug1(NGX_LOG_DEBUG_CORE, file->log, 0,
"temp file: \"%s\"", file->name.data);
if (ngx_create_dir(file->name.data, 0700) == NGX_FILE_ERROR) {
err = ngx_errno;
if (err != NGX_EEXIST) {
ngx_log_error(NGX_LOG_CRIT, file->log, err,
ngx_create_dir_n " \"%s\" failed",
file->name.data);
return NGX_ERROR;
}
}
file->name.data[pos] = '/';
}
return NGX_OK;
}这里分别创建path中的每一级路径。
8. 函数ngx_create_full_path()
ngx_err_t
ngx_create_full_path(u_char *dir, ngx_uint_t access)
{
u_char *p, ch;
ngx_err_t err;
err = 0;
#if (NGX_WIN32)
p = dir + 3;
#else
p = dir + 1;
#endif
for ( /* void */ ; *p; p++) {
ch = *p;
if (ch != '/') {
continue;
}
*p = '\0';
if (ngx_create_dir(dir, access) == NGX_FILE_ERROR) {
err = ngx_errno;
switch (err) {
case NGX_EEXIST:
err = 0;
case NGX_EACCES:
break;
default:
return err;
}
}
*p = '/';
}
return err;
}这里以’/’作为分界符，分别创建每一级路径。
9. 函数ngx_next_temp_number()
ngx_atomic_uint_t
ngx_next_temp_number(ngx_uint_t collision)
{
ngx_atomic_uint_t n, add;
add = collision ? ngx_random_number : 1;
n = ngx_atomic_fetch_add(ngx_temp_number, add);
return n + add;
}这里根据collision的条件，每次对ngx_temp_number增加一个值，然后返回.
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