core/ngx_parse.c(h)文件分析
本章我们介绍一下ngx_parse.c(h)文件，其主要用于解析如下三方面：
-
size单位解析（如K,M等）
-
offset偏移解析(如K、M、G等）
-
时间单位解析
1. ngx_parsh.h头文件
/*
* Copyright (C) Igor Sysoev
* Copyright (C) Nginx, Inc.
*/
#ifndef _NGX_PARSE_H_INCLUDED_
#define _NGX_PARSE_H_INCLUDED_
#include <ngx_config.h>
#include <ngx_core.h>
ssize_t ngx_parse_size(ngx_str_t *line);
off_t ngx_parse_offset(ngx_str_t *line);
ngx_int_t ngx_parse_time(ngx_str_t *line, ngx_uint_t is_sec);
#endif /* _NGX_PARSE_H_INCLUDED_ */这里主要是声明了三个函数，分别用于size解析、offset解析、时间解析。
2. ngx_parse.c源文件
2.1 函数
/*
* Copyright (C) Igor Sysoev
* Copyright (C) Nginx, Inc.
*/
#include <ngx_config.h>
#include <ngx_core.h>
ssize_t
ngx_parse_size(ngx_str_t *line)
{
u_char unit;
size_t len;
ssize_t size, scale, max;
len = line->len;
unit = line->data[len - 1];
switch (unit) {
case 'K':
case 'k':
len--;
max = NGX_MAX_SIZE_T_VALUE / 1024;
scale = 1024;
break;
case 'M':
case 'm':
len--;
max = NGX_MAX_SIZE_T_VALUE / (1024 * 1024);
scale = 1024 * 1024;
break;
default:
max = NGX_MAX_SIZE_T_VALUE;
scale = 1;
}
size = ngx_atosz(line->data, len);
if (size == NGX_ERROR || size > max) {
return NGX_ERROR;
}
size *= scale;
return size;
}在32位操作系统下,NGX_MAX_SIZE_T_VALUE的最大值为0x7FFFFFF，因此这里我们可算出当以K、M为单位时的最大值size的最大值。函数ngx_atosz()用于将字符串转换为ssize_t类型。
2.2 函数ngx_parse_offset()
off_t
ngx_parse_offset(ngx_str_t *line)
{
u_char unit;
off_t offset, scale, max;
size_t len;
len = line->len;
unit = line->data[len - 1];
switch (unit) {
case 'K':
case 'k':
len--;
max = NGX_MAX_OFF_T_VALUE / 1024;
scale = 1024;
break;
case 'M':
case 'm':
len--;
max = NGX_MAX_OFF_T_VALUE / (1024 * 1024);
scale = 1024 * 1024;
break;
case 'G':
case 'g':
len--;
max = NGX_MAX_OFF_T_VALUE / (1024 * 1024 * 1024);
scale = 1024 * 1024 * 1024;
break;
default:
max = NGX_MAX_OFF_T_VALUE;
scale = 1;
}
offset = ngx_atoof(line->data, len);
if (offset == NGX_ERROR || offset > max) {
return NGX_ERROR;
}
offset *= scale;
return offset;
}此函数用于转换offset类型。与ngx_parse_size()函数类似，这里不再赘述。
2.3 函数ngx_parse_time()
ngx_int_t
ngx_parse_time(ngx_str_t *line, ngx_uint_t is_sec)
{
u_char *p, *last;
ngx_int_t value, total, scale;
ngx_int_t max, cutoff, cutlim;
ngx_uint_t valid;
enum {
st_start = 0,
st_year,
st_month,
st_week,
st_day,
st_hour,
st_min,
st_sec,
st_msec,
st_last
} step;
valid = 0;
value = 0;
total = 0;
cutoff = NGX_MAX_INT_T_VALUE / 10;
cutlim = NGX_MAX_INT_T_VALUE % 10;
step = is_sec ? st_start : st_month;
p = line->data;
last = p + line->len;
while (p < last) {
if (*p >= '0' && *p <= '9') {
if (value >= cutoff && (value > cutoff || *p - '0' > cutlim)) {
return NGX_ERROR;
}
value = value * 10 + (*p++ - '0');
valid = 1;
continue;
}
switch (*p++) {
case 'y':
if (step > st_start) {
return NGX_ERROR;
}
step = st_year;
max = NGX_MAX_INT_T_VALUE / (60 * 60 * 24 * 365);
scale = 60 * 60 * 24 * 365;
break;
case 'M':
if (step >= st_month) {
return NGX_ERROR;
}
step = st_month;
max = NGX_MAX_INT_T_VALUE / (60 * 60 * 24 * 30);
scale = 60 * 60 * 24 * 30;
break;
case 'w':
if (step >= st_week) {
return NGX_ERROR;
}
step = st_week;
max = NGX_MAX_INT_T_VALUE / (60 * 60 * 24 * 7);
scale = 60 * 60 * 24 * 7;
break;
case 'd':
if (step >= st_day) {
return NGX_ERROR;
}
step = st_day;
max = NGX_MAX_INT_T_VALUE / (60 * 60 * 24);
scale = 60 * 60 * 24;
break;
case 'h':
if (step >= st_hour) {
return NGX_ERROR;
}
step = st_hour;
max = NGX_MAX_INT_T_VALUE / (60 * 60);
scale = 60 * 60;
break;
case 'm':
if (p < last && *p == 's') {
if (is_sec || step >= st_msec) {
return NGX_ERROR;
}
p++;
step = st_msec;
max = NGX_MAX_INT_T_VALUE;
scale = 1;
break;
}
if (step >= st_min) {
return NGX_ERROR;
}
step = st_min;
max = NGX_MAX_INT_T_VALUE / 60;
scale = 60;
break;
case 's':
if (step >= st_sec) {
return NGX_ERROR;
}
step = st_sec;
max = NGX_MAX_INT_T_VALUE;
scale = 1;
break;
case ' ':
if (step >= st_sec) {
return NGX_ERROR;
}
step = st_last;
max = NGX_MAX_INT_T_VALUE;
scale = 1;
break;
default:
return NGX_ERROR;
}
if (step != st_msec && !is_sec) {
scale *= 1000;
max /= 1000;
}
if (value > max) {
return NGX_ERROR;
}
value *= scale;
if (total > NGX_MAX_INT_T_VALUE - value) {
return NGX_ERROR;
}
total += value;
value = 0;
while (p < last && *p == ' ') {
p++;
}
}
if (!valid) {
return NGX_ERROR;
}
if (!is_sec) {
if (value > NGX_MAX_INT_T_VALUE / 1000) {
return NGX_ERROR;
}
value *= 1000;
}
if (total > NGX_MAX_INT_T_VALUE - value) {
return NGX_ERROR;
}
return total + value;此函数用于将时间解析成秒数或毫秒数（根据函数参数is_sec)。如果解析成毫秒数的话，由于NGX_MAX_INT_T_VALUE表示范围的缘故，一般我们我们设置的最大单位就应该小于st_month。
[参看]
