我已经编写了一个程序,该程序应该使用zlib函数compress()和uncompress()进行压缩,然后解压缩字符串,它的编译效果还不错,但是由于某种原因,当我启动它时,未压缩字符串中的一些符号丢失了-我得到的是“一些”,然后是一些系统符号。有人可以帮我在这里找到错误吗?
#include "string.h"
#include "stdio.h"
#include "stdlib.h"
#include "zlib.h"
int main()
{
const char *istream = "some foo";
ulong destLen = strlen(istream);
char* ostream = malloc(2 * strlen(istream));
int res = compress(ostream, &destLen, istream, destLen + 1);
const char *i2stream = ostream;
char* o2stream = malloc(4 * strlen(istream));
ulong destLen2 = strlen(i2stream);
int des = uncompress(o2stream, &destLen2, i2stream, destLen2);
printf("%s", o2stream);
return 0;
}
检查错误代码!!
luk32:gcc -lz ./zlib.c
luk32:~/projects/tests$ ./a.out
Buffer was too small!
对于很小的输入,压缩通常无效。因此,您对所需缓冲区大小的预测2*strlen(istream)
是一个低估。
“改进”zlib.c
检查出了什么问题:
#include "string.h"
#include "stdio.h"
#include "stdlib.h"
#include "zlib.h"
int main()
{
const char *istream = "some foo";
ulong destLen = strlen(istream);
char* ostream = malloc(2 * strlen(istream));
int res = compress(ostream, &destLen, istream, destLen + 1);
if(res == Z_BUF_ERROR){
printf("Buffer was too small!\n");
return 1;
}
if(res == Z_MEM_ERROR){
printf("Not enough memory for compression!\n");
return 2;
}
}
仔细阅读文档中的“实用程序功能”后。完整正确的代码:
#include "string.h"
#include "stdio.h"
#include "stdlib.h"
#include "zlib.h"
int main()
{
const char *istream = "some foo";
ulong srcLen = strlen(istream)+1; // +1 for the trailing `\0`
ulong destLen = compressBound(srcLen); // this is how you should estimate size
// needed for the buffer
char* ostream = malloc(destLen);
int res = compress(ostream, &destLen, istream, srcLen);
// destLen is now the size of actuall buffer needed for compression
// you don't want to uncompress whole buffer later, just the used part
if(res == Z_BUF_ERROR){
printf("Buffer was too small!\n");
return 1;
}
if(res == Z_MEM_ERROR){
printf("Not enough memory for compression!\n");
return 2;
}
const char *i2stream = ostream;
char* o2stream = malloc(srcLen);
ulong destLen2 = destLen; //destLen is the actual size of the compressed buffer
int des = uncompress(o2stream, &srcLen, i2stream, destLen2);
printf("%s\n", o2stream);
return 0;
}
测试:
luk32:gcc -lz ./zlib.c
luk32:~/projects/tests$ ./a.out
some foo
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