C语言压缩文件和校验文件完整性 C语言压缩文件和用MD5算法校验文件完整性的实例教程
hzy3774 人气:0想了解C语言压缩文件和用MD5算法校验文件完整性的实例教程的相关内容吗，hzy3774在本文为您仔细讲解C语言压缩文件和校验文件完整性的相关知识和一些Code实例，欢迎阅读和指正，我们先划重点：C语言,压缩,文件,MD5，下面大家一起来学习吧。
使用lzma SDK对7z文件简单解压缩
有时候我们只需要单纯对lzma算法压缩的7z文件进行解压，有时需要在嵌入式设备上解压，使用p7zip虽然支持多种格式，但是不容易裁剪，使用lzma SDK是首选：
可以在这里找到各种版本：http://zh.sourceforge.jp/projects/sfnet_sevenzip/releases/
我下载了4.65版本，这个对文件名编码支持没有9.20的好，中文可能有问题，但是我的需求不需要支持中文文件名，所以足够用了。
解压后先看一下7z这个工程，这个示例只有文件解压操作，仿照就可以写一个更加精简的解压函数：
需要的文件可以参考实例：
修改7zMain.c即可。
我们的目的是写一个函数extract7z，接收参数是7z文件路径，输出文件路径，便可执行全部解压。
主要调用函数：
SRes SzArEx_Open(CSzArEx *p, ILookInStream *inStream, ISzAlloc *allocMain, ISzAlloc *allocTemp); SRes SzAr_Extract( const CSzArEx *p, ILookInStream *inStream, UInt32 fileIndex, UInt32 *blockIndex, Byte **outBuffer, size_t *outBufferSize, size_t *offset, size_t *outSizeProcessed, ISzAlloc *allocMain, ISzAlloc *allocTemp);
我们先在Windows下编译：
完整代码如下：
/* 7zMain.c - Test application for 7z Decoder
*/
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#define LOGD printf
#define LOGE printf
#include "7zCrc.h"
#include "7zFile.h"
#include "7zVersion.h"
#include "7zAlloc.h"
#include "7zExtract.h"
#include "7zIn.h"
int MY_CDECL extract7z(const char* srcFile, const char* dstPath)
{
CFileInStream archiveStream;
CLookToRead lookStream;
CSzArEx db;
SRes res;
ISzAlloc allocImp;
ISzAlloc allocTempImp;
char outPath[1024] = { 0 };
LOGD("7z ANSI-C Decoder " MY_VERSION_COPYRIGHT_DATE "\n");
if (InFile_Open(&archiveStream.file, srcFile)) {//open 7z file
LOGE("can not open input file\n");
return 1;
}
FileInStream_CreateVTable(&archiveStream);
LookToRead_CreateVTable(&lookStream, False);
lookStream.realStream = &archiveStream.s;
LookToRead_Init(&lookStream);
allocImp.Alloc = SzAlloc;
allocImp.Free = SzFree;
allocTempImp.Alloc = SzAllocTemp;
allocTempImp.Free = SzFreeTemp;
CrcGenerateTable();
SzArEx_Init(&db);
res = SzArEx_Open(&db, &lookStream.s, &allocImp, &allocTempImp);
if(res == SZ_OK)
{
Int32 i;
UInt32 blockIndex = 0xFFFFFFFF; /* it can have any value before first call (if outBuffer = 0) */
Byte *outBuffer = 0; /* it must be 0 before first call for each new archive. */
size_t outBufferSize = 0; /* it can have any value before first call (if outBuffer = 0) */
LOGD("Total file/directory count[%d]\n", db.db.NumFiles);
for (i = db.db.NumFiles - 1; i >= 0; i--) {
size_t offset;
size_t outSizeProcessed;
CSzFileItem *f = db.db.Files + i;
strcpy(outPath, dstPath);
strcat(outPath, "/");
strcat(outPath, f->Name);
if (f->IsDir) { //dir
LOGD("dir [%s]\n", outPath);
mkdir(outPath);
continue;
}else{ //file
LOGD("file [%s]\n", outPath);
res = SzAr_Extract(&db, &lookStream.s, i, &blockIndex,
&outBuffer, &outBufferSize, &offset, &outSizeProcessed,
&allocImp, &allocTempImp);
if (res != SZ_OK){
break;
}else{
CSzFile outFile;
size_t processedSize;
if (OutFile_Open(&outFile, outPath)) {
LOGE("can not open output file\n");
res = SZ_ERROR_FAIL;
break;
}
processedSize = outSizeProcessed;
if (File_Write(&outFile, outBuffer + offset, &processedSize)
!= 0 || processedSize != outSizeProcessed) {
LOGE("can not write output file\n");
res = SZ_ERROR_FAIL;
break;
}
if (File_Close(&outFile)) {
LOGE("can not close output file\n");
res = SZ_ERROR_FAIL;
break;
}
}
}
}
IAlloc_Free(&allocImp, outBuffer);
}
SzArEx_Free(&db, &allocImp);
File_Close(&archiveStream.file);
if (res == SZ_OK)
{
LOGD("Everything is Ok\n");
return 0;
}
if (res == SZ_ERROR_UNSUPPORTED
)
LOGE("decoder doesn't support this archive\n");
else if (res == SZ_ERROR_MEM
)
LOGE("can not allocate memory\n");
else if (res == SZ_ERROR_CRC
)
LOGE("CRC error\n");
else
LOGE("ERROR #%d\n", res);
return 1;
}
int main(int numargs, char *args[])
{
return extract7z(args[1], args[2]);
}
我用的是Eclipse，使用Mingw编译。
执行效果，能正确解压。
这样的解压只能适用简单的解压，不支持加密，参数2的输出文件路径中的所有文件夹都必须存在，压缩包中文件夹不需要存在，解压时会自动创建。
压缩包中的文件夹不能为中文，否则乱码。
使用MD5算法验证文件完整性或密码正确性
MD5即Message-Digest Algorithm 5（信息-摘要算法5），用于确保信息传输完整一致。是计算机广泛使用的杂凑算法之一（又译摘要算法、哈希算法），主流编程语言普遍已有MD5实现。
将数据（如汉字）运算为另一固定长度值，是杂凑算法的基础原理，MD5的前身有MD2、MD3和MD4。
MD5的作用是让大容量信息在用数字签名软件签署私人密钥前被"压缩"成一种保密的格式（就是把一个任意长度的字节串变换成一定长的十六进制数字串）。
MD5在实际应用中通常有两种用法，一种是计算一个字符串的MD5值，常用于密码相关的操作；另一种是用于计算一个文件的MD5值，一般用于网络传输中验证文件是否出错。
下面是C语言的MD5计算程序，来自Stardict，网上流行的代码都大同小异：
md5.h
#ifndef MD5_H
#define MD5_H
#ifdef __cplusplus
extern "C"
{
#endif /* __cplusplus */
#ifdef HAVE_CONFIG_H
# include "config.h"
#endif
#ifdef HAVE_STDINT_H
#include <stdint.h>
typedef uint32_t uint32;
#else
/* A.Leo.: this wont work on 16 bits platforms ;) */
typedef unsigned uint32;
#endif
#define MD5_FILE_BUFFER_LEN 1024
struct MD5Context {
uint32 buf[4];
uint32 bits[2];
unsigned char in[64];
};
void MD5Init(struct MD5Context *context);
void MD5Update(struct MD5Context *context, unsigned char const *buf,
unsigned len);
void MD5Final(unsigned char digest[16], struct MD5Context *context);
void MD5Transform(uint32 buf[4], uint32 const in[16]);
int getBytesMD5(const unsigned char* src, unsigned int length, char* md5);
int getStringMD5(const char* src, char* md5);
int getFileMD5(const char* path, char* md5);
/*
* This is needed to make RSAREF happy on some MS-DOS compilers.
*/
typedef struct MD5Context MD5_CTX;
#ifdef __cplusplus
}
#endif /* __cplusplus */
#endif /* !MD5_H */
源文件：
md5.c
#include <string.h> /* for memcpy() */
#include <stdio.h>
#include "md5.h"
#ifndef HIGHFIRST
#define byteReverse(buf, len) /* Nothing */
#else
void byteReverse(unsigned char *buf, unsigned longs);
#ifndef ASM_MD5
/*
* Note: this code is harmless on little-endian machines.
*/
void byteReverse(unsigned char *buf, unsigned longs)
{
uint32 t;
do {
t = (uint32) ((unsigned) buf[3] << 8 | buf[2]) << 16 |
((unsigned) buf[1] << 8 | buf[0]);
*(uint32 *) buf = t;
buf += 4;
}while (--longs);
}
#endif
#endif
static void putu32(uint32 data, unsigned char *addr) {
addr[0] = (unsigned char) data;
addr[1] = (unsigned char) (data >> 8);
addr[2] = (unsigned char) (data >> 16);
addr[3] = (unsigned char) (data >> 24);
}
/*
* Start MD5 accumulation. Set bit count to 0 and buffer to mysterious
* initialization constants.
*/
void MD5Init(struct MD5Context *ctx) {
ctx->buf[0] = 0x67452301;
ctx->buf[1] = 0xefcdab89;
ctx->buf[2] = 0x98badcfe;
ctx->buf[3] = 0x10325476;
ctx->bits[0] = 0;
ctx->bits[1] = 0;
}
/*
* Update context to reflect the concatenation of another buffer full
* of bytes.
*/
void MD5Update(struct MD5Context *ctx, unsigned char const *buf, unsigned len) {
uint32 t;
/* Update bitcount */
t = ctx->bits[0];
if ((ctx->bits[0] = t + ((uint32) len << 3)) < t)
ctx->bits[1]++; /* Carry from low to high */
ctx->bits[1] += len >> 29;
t = (t >> 3) & 0x3f; /* Bytes already in shsInfo->data */
/* Handle any leading odd-sized chunks */
if (t) {
unsigned char *p = (unsigned char *) ctx->in + t;
t = 64 - t;
if (len < t) {
memcpy(p, buf, len);
return;
}
memcpy(p, buf, t);
byteReverse(ctx->in, 16);
MD5Transform(ctx->buf, (uint32 *) ctx->in);
buf += t;
len -= t;
}
/* Process data in 64-byte chunks */
while (len >= 64) {
memcpy(ctx->in, buf, 64);
byteReverse(ctx->in, 16);
MD5Transform(ctx->buf, (uint32 *) ctx->in);
buf += 64;
len -= 64;
}
/* Handle any remaining bytes of data. */
memcpy(ctx->in, buf, len);
}
/*
* Final wrapup - pad to 64-byte boundary with the bit pattern
* 1 0* (64-bit count of bits processed, MSB-first)
*/
void MD5Final(unsigned char digest[16], struct MD5Context *ctx) {
unsigned count;
unsigned char *p;
/* Compute number of bytes mod 64 */
count = (ctx->bits[0] >> 3) & 0x3F;
/* Set the first char of padding to 0x80. This is safe since there is
always at least one byte free */
p = ctx->in + count;
*p++ = 0x80;
/* Bytes of padding needed to make 64 bytes */
count = 64 - 1 - count;
/* Pad out to 56 mod 64 */
if (count < 8) {
/* Two lots of padding: Pad the first block to 64 bytes */
memset(p, 0, count);
byteReverse(ctx->in, 16);
MD5Transform(ctx->buf, (uint32 *) ctx->in);
/* Now fill the next block with 56 bytes */
memset(ctx->in, 0, 56);
} else {
/* Pad block to 56 bytes */
memset(p, 0, count - 8);
} byteReverse(ctx->in, 14);
/* Append length in bits and transform */
//((uint32 *) ctx->in)[14] = ctx->bits[0];
//((uint32 *) ctx->in)[15] = ctx->bits[1];
putu32(ctx->bits[0], ctx->in + 56);
putu32(ctx->bits[1], ctx->in + 60);
MD5Transform(ctx->buf, (uint32 *) ctx->in);
byteReverse((unsigned char *) ctx->buf, 4);
memcpy(digest, ctx->buf, 16);
memset(ctx, 0, sizeof(*ctx)); /* In case it's sensitive */
}
#ifndef ASM_MD5
/* The four core functions - F1 is optimized somewhat */
/* #define F1(x, y, z) (x & y | ~x & z) */
#define F1(x, y, z) (z ^ (x & (y ^ z)))
#define F2(x, y, z) F1(z, x, y)
#define F3(x, y, z) (x ^ y ^ z)
#define F4(x, y, z) (y ^ (x | ~z))
/* This is the central step in the MD5 algorithm. */
#define MD5STEP(f, w, x, y, z, data, s) \
( w += f(x, y, z) + data, w = w<<s | w>>(32-s), w += x )
/*
* The core of the MD5 algorithm, this alters an existing MD5 hash to
* reflect the addition of 16 longwords of new data. MD5Update blocks
* the data and converts bytes into longwords for this routine.
*/
void MD5Transform(uint32 buf[4], uint32 const in[16]) {
register uint32 a, b, c, d;
a = buf[0];
b = buf[1];
c = buf[2];
d = buf[3];
MD5STEP(F1, a, b, c, d, in[0] + 0xd76aa478, 7);
MD5STEP(F1, d, a, b, c, in[1] + 0xe8c7b756, 12);
MD5STEP(F1, c, d, a, b, in[2] + 0x242070db, 17);
MD5STEP(F1, b, c, d, a, in[3] + 0xc1bdceee, 22);
MD5STEP(F1, a, b, c, d, in[4] + 0xf57c0faf, 7);
MD5STEP(F1, d, a, b, c, in[5] + 0x4787c62a, 12);
MD5STEP(F1, c, d, a, b, in[6] + 0xa8304613, 17);
MD5STEP(F1, b, c, d, a, in[7] + 0xfd469501, 22);
MD5STEP(F1, a, b, c, d, in[8] + 0x698098d8, 7);
MD5STEP(F1, d, a, b, c, in[9] + 0x8b44f7af, 12);
MD5STEP(F1, c, d, a, b, in[10] + 0xffff5bb1, 17);
MD5STEP(F1, b, c, d, a, in[11] + 0x895cd7be, 22);
MD5STEP(F1, a, b, c, d, in[12] + 0x6b901122, 7);
MD5STEP(F1, d, a, b, c, in[13] + 0xfd987193, 12);
MD5STEP(F1, c, d, a, b, in[14] + 0xa679438e, 17);
MD5STEP(F1, b, c, d, a, in[15] + 0x49b40821, 22);
MD5STEP(F2, a, b, c, d, in[1] + 0xf61e2562, 5);
MD5STEP(F2, d, a, b, c, in[6] + 0xc040b340, 9);
MD5STEP(F2, c, d, a, b, in[11] + 0x265e5a51, 14);
MD5STEP(F2, b, c, d, a, in[0] + 0xe9b6c7aa, 20);
MD5STEP(F2, a, b, c, d, in[5] + 0xd62f105d, 5);
MD5STEP(F2, d, a, b, c, in[10] + 0x02441453, 9);
MD5STEP(F2, c, d, a, b, in[15] + 0xd8a1e681, 14);
MD5STEP(F2, b, c, d, a, in[4] + 0xe7d3fbc8, 20);
MD5STEP(F2, a, b, c, d, in[9] + 0x21e1cde6, 5);
MD5STEP(F2, d, a, b, c, in[14] + 0xc33707d6, 9);
MD5STEP(F2, c, d, a, b, in[3] + 0xf4d50d87, 14);
MD5STEP(F2, b, c, d, a, in[8] + 0x455a14ed, 20);
MD5STEP(F2, a, b, c, d, in[13] + 0xa9e3e905, 5);
MD5STEP(F2, d, a, b, c, in[2] + 0xfcefa3f8, 9);
MD5STEP(F2, c, d, a, b, in[7] + 0x676f02d9, 14);
MD5STEP(F2, b, c, d, a, in[12] + 0x8d2a4c8a, 20);
MD5STEP(F3, a, b, c, d, in[5] + 0xfffa3942, 4);
MD5STEP(F3, d, a, b, c, in[8] + 0x8771f681, 11);
MD5STEP(F3, c, d, a, b, in[11] + 0x6d9d6122, 16);
MD5STEP(F3, b, c, d, a, in[14] + 0xfde5380c, 23);
MD5STEP(F3, a, b, c, d, in[1] + 0xa4beea44, 4);
MD5STEP(F3, d, a, b, c, in[4] + 0x4bdecfa9, 11);
MD5STEP(F3, c, d, a, b, in[7] + 0xf6bb4b60, 16);
MD5STEP(F3, b, c, d, a, in[10] + 0xbebfbc70, 23);
MD5STEP(F3, a, b, c, d, in[13] + 0x289b7ec6, 4);
MD5STEP(F3, d, a, b, c, in[0] + 0xeaa127fa, 11);
MD5STEP(F3, c, d, a, b, in[3] + 0xd4ef3085, 16);
MD5STEP(F3, b, c, d, a, in[6] + 0x04881d05, 23);
MD5STEP(F3, a, b, c, d, in[9] + 0xd9d4d039, 4);
MD5STEP(F3, d, a, b, c, in[12] + 0xe6db99e5, 11);
MD5STEP(F3, c, d, a, b, in[15] + 0x1fa27cf8, 16);
MD5STEP(F3, b, c, d, a, in[2] + 0xc4ac5665, 23);
MD5STEP(F4, a, b, c, d, in[0] + 0xf4292244, 6);
MD5STEP(F4, d, a, b, c, in[7] + 0x432aff97, 10);
MD5STEP(F4, c, d, a, b, in[14] + 0xab9423a7, 15);
MD5STEP(F4, b, c, d, a, in[5] + 0xfc93a039, 21);
MD5STEP(F4, a, b, c, d, in[12] + 0x655b59c3, 6);
MD5STEP(F4, d, a, b, c, in[3] + 0x8f0ccc92, 10);
MD5STEP(F4, c, d, a, b, in[10] + 0xffeff47d, 15);
MD5STEP(F4, b, c, d, a, in[1] + 0x85845dd1, 21);
MD5STEP(F4, a, b, c, d, in[8] + 0x6fa87e4f, 6);
MD5STEP(F4, d, a, b, c, in[15] + 0xfe2ce6e0, 10);
MD5STEP(F4, c, d, a, b, in[6] + 0xa3014314, 15);
MD5STEP(F4, b, c, d, a, in[13] + 0x4e0811a1, 21);
MD5STEP(F4, a, b, c, d, in[4] + 0xf7537e82, 6);
MD5STEP(F4, d, a, b, c, in[11] + 0xbd3af235, 10);
MD5STEP(F4, c, d, a, b, in[2] + 0x2ad7d2bb, 15);
MD5STEP(F4, b, c, d, a, in[9] + 0xeb86d391, 21);
buf[0] += a;
buf[1] += b;
buf[2] += c;
buf[3] += d;
}
/*
* get MD5 of a byte buffer
*/
int getBytesMD5(const unsigned char* src, unsigned int length, char* md5) {
unsigned char i = 0;
unsigned char md5Bytes[16] = { 0 };
MD5_CTX context;
if (src == NULL || md5 == NULL)
{
return -1;
}
MD5Init(&context);
MD5Update(&context, src, length);
MD5Final(md5Bytes, &context);
for (i = 0; i < 16; i++) {
sprintf(md5, "%02X", md5Bytes[i]);
md5 += 2;
}
*md5 = '\0';
return 0;
}
/*
* get MD5 for a string
*/
int getStringMD5(const char* src, char* md5) {
return getBytesMD5((unsigned char*) src, strlen((char*) src), md5);
}
/**
* get MD5 of a file
*/
int getFileMD5(const char* path, char* md5) {
FILE* fp = NULL;
unsigned char buffer[MD5_FILE_BUFFER_LEN] = { 0 };
int count = 0;
MD5_CTX context;
unsigned char md5Bytes[16] = { 0 };
int i;
if (path == NULL || md5 == NULL) {
return -1;
}
fp = fopen(path, "rb");
if (fp == NULL) {
return -1;
}
MD5Init(&context);
while ((count = fread(buffer, 1, MD5_FILE_BUFFER_LEN, fp)) > 0) {
MD5Update(&context, buffer, count);
}
MD5Final(md5Bytes, &context);
for (i = 0; i < 16; i++) {
sprintf(md5, "%02X", md5Bytes[i]);
md5 += 2;
}
*md5 = '\0';
return 0;
}
#endif
下面是调用函数计算MD5的代码：
main.c
#include <stdio.h>
#include <string.h>
#include "md5.h"
int main(int c, char** v){
char buffer[128];
getStringMD5("hello world", buffer);
printf("%s\n", buffer);
getFileMD5("hello.pdf", buffer);
printf("%s\n", buffer);
return 0;
}
计算无误：
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