是否可以在不提取Objective-C文件的情況下讀取壓縮文件？

Question

我正在構建一個應用程序，它需要在不提取文件的情況下讀取zip文件內的文件。有沒有這種功能的圖書館，或者你能給我一些關於如何解決它的想法嗎？

Answer 1

您可以一次解壓縮一個數據緩衝區，然後通讀它，假定文件是文本，並且可以用增量方式解析它（例如，用於處理的XML數據一個SAX解析器）。

這是我寫的一個例程，它從zip-stream中提取數據，並一次打印出一行。您可以修改它來打印或解析N字符。或者你可以將行添加到行緩衝區，並且一次處理/解析一大塊行。

這使用zlib，如果這個代碼是對你有用，可隨時使用它：

# 
# compile with -lz option in order to link in the zlib library 
# 

#include <zlib.h> 

#define Z_CHUNK 2097152 

int unzipFile(const char *fName) 
{ 
    z_stream zStream; 
    char *zRemainderBuf = malloc(1); 
    unsigned char zInBuf[Z_CHUNK]; 
    unsigned char zOutBuf[Z_CHUNK]; 
    char zLineBuf[Z_CHUNK]; 
    unsigned int zHave, zBufIdx, zBufOffset, zOutBufIdx; 
    int zError; 
    FILE *inFp = fopen(fName, "rbR"); 

    if (!inFp) { fprintf(stderr, "could not open file: %s\n", fName); return EXIT_FAILURE; } 

    zStream.zalloc = Z_NULL; 
    zStream.zfree = Z_NULL; 
    zStream.opaque = Z_NULL; 
    zStream.avail_in = 0; 
    zStream.next_in = Z_NULL; 

    zError = inflateInit2(&zStream, (15+32)); /* cf. http://www.zlib.net/manual.html */ 
    if (zError != Z_OK) { fprintf(stderr, "could not initialize z-stream\n"); return EXIT_FAILURE; } 

    *zRemainderBuf = '\0'; 
    do { 
     zStream.avail_in = fread(zInBuf, 1, Z_CHUNK, inFp); 
     if (zStream.avail_in == 0) 
      break; 
     zStream.next_in = zInBuf; 
     do { 
      zStream.avail_out = Z_CHUNK; 
      zStream.next_out = zOutBuf; 
      zError = inflate(&zStream, Z_NO_FLUSH); 
      switch (zError) { 
       case Z_NEED_DICT: { fprintf(stderr, "Z-stream needs dictionary!\n"); return EXIT_FAILURE; } 
       case Z_DATA_ERROR: { fprintf(stderr, "Z-stream suffered data error!\n"); return EXIT_FAILURE; } 
       case Z_MEM_ERROR: { fprintf(stderr, "Z-stream suffered memory error!\n"); return EXIT_FAILURE; } 
      } 
      zHave = Z_CHUNK - zStream.avail_out; 
      zOutBuf[zHave] = '\0'; 

      /* copy remainder buffer onto line buffer, if not NULL */ 
      if (zRemainderBuf) { 
       strncpy(zLineBuf, zRemainderBuf, strlen(zRemainderBuf)); 
       zBufOffset = strlen(zRemainderBuf); 
      } 
      else 
       zBufOffset = 0; 

      /* read through zOutBuf for newlines */ 
      for (zBufIdx = zBufOffset, zOutBufIdx = 0; zOutBufIdx < zHave; zBufIdx++, zOutBufIdx++) { 
       zLineBuf[zBufIdx] = zOutBuf[zOutBufIdx]; 
       if (zLineBuf[zBufIdx] == '\n') { 
        zLineBuf[zBufIdx] = '\0'; 
        zBufIdx = -1; 
        fprintf(stdout, "%s\n", zLineBuf); 
       } 
      } 

      /* copy some of line buffer onto the remainder buffer, if there are remnants from the z-stream */ 
      if (strlen(zLineBuf) > 0) { 
       if (strlen(zLineBuf) > strlen(zRemainderBuf)) { 
        /* to minimize the chance of doing another (expensive) malloc, we double the length of zRemainderBuf */ 
        free(zRemainderBuf); 
        zRemainderBuf = malloc(strlen(zLineBuf) * 2); 
       } 
       strncpy(zRemainderBuf, zLineBuf, zBufIdx); 
       zRemainderBuf[zBufIdx] = '\0'; 
      } 
     } while (zStream.avail_out == 0); 
    } while (zError != Z_STREAM_END); 

    /* close gzip stream */ 
    zError = inflateEnd(&zStream); 
    if (zError != Z_OK) { 
     fprintf(stderr, "could not close z-stream!\n"); 
     return EXIT_FAILURE; 
    } 
    if (zRemainderBuf) 
     free(zRemainderBuf); 

    fclose(inFp); 

    return EXIT_SUCCESS; 
}