c语言http请求解析表单内容

cgi.h

#ifndef CGI_H
#define CGI_H

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
typedef struct Node{
char *name;
char *value;
struct Node *next;
}Node;
typedef struct Index{
Node *head;
char *buffer;
}Index;
Index *get_input();
void free_input(Index *);
Node *analyze(char *);
Node *analy_a(char *);
Node *analy_m(char *, char *);
char *get_value(Node *, char *);
char fun1(char);
#endif

get_input.c

#include "cgi.h"

Index *get_input() {
//获得表单发送方法
char *get_method = getenv("REQUEST_METHOD");
Index *input = (Index *)malloc(sizeof(Index));
Node *head;
char *buffer;
if (strcmp(get_method,"GET") == 0) {
char *get_str = getenv("QUERY_STRING");
if (get_str == NULL || *get_str == 0) {
return NULL;
}
//get方法，通过环境变量得到内容
buffer = (char *)malloc(strlen(get_str) + 1);
strcpy(buffer, get_str);
//对内容进行解析，以链表的形式存在
head = analy_a(buffer);
} else if (strcmp(get_method,"POST") == 0){
int get_len = atoi(getenv("CONTENT_LENGTH"));
if (get_len == 0) {
return NULL;
}
//post方法，通过标准输入读取内容
buffer = (char *)malloc(get_len + 1);
memset(buffer,0,get_len + 1);
int n =fread(buffer, 1,get_len, stdin);
if (n != get_len) {
fprintf(stderr,"Read error!");
}
head = analyze(buffer);
}
//链表头
input -> head = head;
//接受到的字符串
input -> buffer = buffer;
return input;
}

analyze.c

#include "cgi.h"
//post方法获取的内容进行解析
Node *analyze(char *buffer) 
{
//获取内容格式
char *c_type = getenv("CONTENT_TYPE");
char *bound;
fprintf(stderr,"debug:c_type is %s\n",c_type);
if (strcmp("application/x-www-form-urlencoded",c_type) == 0) {
//该格式表明获取内容为"name=value"形式
return analy_a(buffer);
} else if (strcmp("text/plain", c_type) == 0) {
//此种编码格式暂不讨论
} else {
//编码格式为multipart/form-data，适用大流量数据传送
//获取等号后面的分隔符
bound = index(c_type,'=') + 1;
fprintf(stderr,"debug:bound is %s\n",bound);
return analy_m(buffer, bound);
}
}

analy_a.c

#include "cgi.h"
//编码格式为'application/x-www-form-urlencoded'的内容
Node *analy_a(char *buffer) 
{
//创建第一个节点
Node *head = (Node *)malloc(sizeof(Node));
Node *temp = head;
temp -> name = buffer;
char *b_temp = buffer;
//通过移动、改变部分字符来分离字符串
while (*buffer != 0) {
if (*buffer == '=') {
//'='，则表示name已经结束，value将开始
*b_temp = 0;
temp -> value = b_temp + 1;
}else if (*buffer == '+') {
//'+'代表空格
*b_temp = ' ';
}else if (*buffer == '%') {
//'%'则紧跟两位十六进制表示的特殊字符
*b_temp = fun1(*(buffer + 1)) * 16 + fun1(*(buffer + 2));
buffer += 2;
}
else if (*buffer == '&') {
//'&'表示value已经结束，name即将开始
*b_temp = 0;
//重新申请内存，存储新内容地址
temp -> next = (Node *)malloc(sizeof(Node));
temp = temp -> next;
temp -> name = b_temp + 1;
}else {
*b_temp = *buffer;
}
buffer++;
b_temp++;
}
//最后一个结束符
*b_temp = 0;
return head;
}

analy_m.c

#include "cgi.h"
//编码格式为'multipart/form-data'的内容
Node *analy_m(char *buffer, char *bound) 
{
char *start;
char *end;
//第一个节点
Node *head = (Node*)malloc(sizeof(Node));
Node *temp = head;
fprintf(stderr,"debug:buffer is %s\n", buffer);
//开始解析内容，name在两个双引号之间(详见编码格式)
temp -> name = index(buffer, '"') + 1;
end = index(temp -> name, '"');
*end = 0;
fprintf(stderr,"debug:temp->name is %s\n", temp -> name);
//中间间隔了两个"\r\n"
temp -> value = end + 5;
buffer = strstr(temp -> value, bound);
//到下一个间隔符，上面间隔两个"\r\n"
*(buffer - 4) = 0;
fprintf(stderr,"debug:temp->valu is %s\n", temp -> value);
while ((start = strstr(buffer,"name=")) != NULL) {
//循环获取name与value地址，直到没有name为止
temp -> next = (Node *)malloc(sizeof(Node));
temp = temp -> next;
temp -> name = index(start, '"') + 1;
end = index(temp -> name, '"');
*end = 0;
fprintf(stderr,"debug:temp->name is %s\n", temp -> name);
temp -> value = end + 5;
buffer = strstr(temp -> value, bound);
*(buffer - 4) = 0;
fprintf(stderr,"debug:temp->valu is %s\n", temp -> value);
}
return head;
}

fun1.c

//将十六进制字符转化为十进制数
char fun1(char ch)
{
char buffer;
if (ch < 'A') {
buffer = ch - 48;
}else if (ch < 'a'){
buffer = ch - 55;
}else {
buffer = ch - 87;
}
return buffer;
}

get_value.c

#include "cgi.h"
//根据name获取相应的value
char *get_value(Node *head, char *name)
{
Node *p;
while (head != NULL) {
if (strcmp(head -> name, name) == 0) {
return head -> value;
}
p = head -> next;
head = p;
}
return NULL;
}

free_input.c

#include "cgi.h"
//释放动态获取的内存
void free_input(Index *index)
{
Node *temp = index -> head;
Node *p;
while (temp != NULL) {
p = temp -> next;
free(temp);
temp = p;
}
free(index -> buffer);
free(index);
}

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