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缘由：
学习需要
正文：
参考解答：
字符串压缩
#include <stdio.h>#include <string.h> // for strlen#include <assert.h>#include "zlib.h"/**/int main(int argc, char* argv[]){ // original string len = 36 char a[50] = "Hello Hello Hello Hello Hello Hello!"; // placeholder for the compressed (deflated) version of "a" char b[50]; // placeholder for the UNcompressed (inflated) version of "b" char c[50]; printf("sizeof(a) = %d\n", sizeof(a)); printf("sizeof(b) = %d\n", sizeof(b)); printf("sizeof(c) = %d\n", sizeof(c)); printf("Original size is: %lu\n", strlen(a)); printf("Original string is: %s\n", a); printf("\n----------\n\n"); // STEP 1. // deflate a into b. (that is, compress a into b) // zlib struct z_stream defstream; defstream.zalloc = Z_NULL; defstream.zfree = Z_NULL; defstream.opaque = Z_NULL; // setup "a" as the input and "b" as the compressed output defstream.avail_in = (uInt)strlen(a)+1; // size of input, string + terminator defstream.next_in = (Bytef *)a; // input char array defstream.avail_out = (uInt)sizeof(b); // size of output defstream.next_out = (Bytef *)b; // output char array // the actual compression work. deflateInit(&defstream, Z_BEST_COMPRESSION); deflate(&defstream, Z_FINISH); deflateEnd(&defstream); // This is one way of getting the size of the output printf("Compressed size is: %lu\n", strlen(b)); printf("Compressed string is: %s\n", b); printf("\n----------\n\n"); // STEP 2. // inflate b into c // zlib struct z_stream infstream; infstream.zalloc = Z_NULL; infstream.zfree = Z_NULL; infstream.opaque = Z_NULL; // setup "b" as the input and "c" as the compressed output infstream.avail_in = (uInt)((char*)defstream.next_out - b); // size of input infstream.next_in = (Bytef *)b; // input char array infstream.avail_out = (uInt)sizeof(c); // size of output infstream.next_out = (Bytef *)c; // output char array // the actual DE-compression work. inflateInit(&infstream); inflate(&infstream, Z_NO_FLUSH); inflateEnd(&infstream); printf("Uncompressed size is: %lu\n", strlen(c)); printf("Uncompressed string is: %s\n", c); // make sure uncompressed is exactly equal to original. assert(strcmp(a,c)==0); return 0;} |
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#include <stdio.h>#include <zlib.h>#include <stdlib.h>#include <string.h>/* CHUNK is the size of the memory chunk used by the zlib routines. */#define CHUNK 0x4000/* The following macro calls a zlib routine and checks the return value. If the return value ("status") is not OK, it prints an error message and exits the program. Zlib's error statuses are all less than zero. */#define CALL_ZLIB(x) { \ int status; \ status = x; \ if (status < 0) { \ fprintf (stderr, \ "%s:%d: %s returned a bad status of %d.\n", \ __FILE__, __LINE__, #x, status); \ exit (EXIT_FAILURE); \ } \ }/* These are parameters to deflateInit2. See http://zlib.net/manual.html for the exact meanings. */#define windowBits 15#define GZIP_ENCODING 16static void strm_init (z_stream * strm){ strm->zalloc = Z_NULL; strm->zfree = Z_NULL; strm->opaque = Z_NULL; CALL_ZLIB (deflateInit2 (strm, Z_DEFAULT_COMPRESSION, Z_DEFLATED, windowBits | GZIP_ENCODING, 8, Z_DEFAULT_STRATEGY));}/* Example text to print out. */static const char * message ="Shall I compare thee to a summer's day?\n""Thou art more lovely and more temperate:\n""Rough winds do shake the darling buds of May,\n""And summer's lease hath all too short a date;\n""And summer's lease hath all too short a date;\n""And summer's lease hath all too short a date;\n""And summer's lease hath all too short a date;\n""And summer's lease hath all too short a date;\n""And summer's lease hath all too short a date;\n""And summer's lease hath all too short a date;\n""And summer's lease hath all too short a date;\n""And summer's lease hath all too short a date;\n""And summer's lease hath all too short a date;\n""And summer's lease hath all too short a date;\n""And summer's lease hath all too short a date;\n""And summer's lease hath all too short a date;\n""And summer's lease hath all too short a date;\n""And summer's lease hath all too short a date;\n""And summer's lease hath all too short a date;\n""And summer's lease hath all too short a date;\n""And summer's lease hath all too short a date;\n""And summer's lease hath all too short a date;\n""And summer's lease hath all too short a date;\n";/*$ ./a.out | wc 2 6 160$ ./a.out | gzip -d | wc 23 204 1047 *//*static const char * message ="Shall I compare thee to a summer's day?\n""Thou art more lovely and more temperate:\n""Rough winds do shake the darling buds of May,\n""And summer's lease hath all too short a date;\n";$ ./a.out | wc 1 5 150$ ./a.out | gzip -d | wc 4 33 173 */int main (){ unsigned char out[CHUNK]; z_stream strm; strm_init (& strm); strm.next_in = (unsigned char *) message; strm.avail_in = strlen (message); do { int have; strm.avail_out = CHUNK; strm.next_out = out; CALL_ZLIB (deflate (& strm, Z_FINISH)); have = CHUNK - strm.avail_out; fwrite (out, sizeof (char), have, stdout); } while (strm.avail_out == 0); deflateEnd (& strm); return 0;}/*$ gcc compress_with_zlib.c -lz*/ |
参考链接：
- http://zlib.net/manual.html
- http://zlib.net/zlib_how.html
- https://gist.githubusercontent.com/arq5x/5315739/raw/9a7e9569779d7771b643dc1840cbbea16a9b933f/zlib-example.cpp
- https://stackoverflow.com/questions/7540259/deflate-and-inflate-zlib-h-in-c
- https://www.lemoda.net/c/zlib-open-write/
- https://stackoverflow.com/questions/6781575/unable-to-build-zpipe-c-zlib-sample-program
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