C 语言中的 deflate 和 inflate (zlib.h)

发布于 2024-12-06 10:48:42 字数 1217 浏览 1 评论 0原文

我正在尝试实现 zlib.h deflate 和 inflate 函数来压缩和解压缩 char 数组（而不是文件）。

我想知道以下语法是否正确？我是否遗漏了某些内容或错误地定义了某些内容？

char a[50] = "Hello World!";
char b[50];
char c[50];

// deflate
// zlib struct
z_stream defstream;
defstream.zalloc = Z_NULL;
defstream.zfree = Z_NULL;
defstream.opaque = Z_NULL;
defstream.avail_in = (uInt)sizeof(a); // size of input
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

deflateInit(&defstream, Z_DEFAULT_COMPRESSION);
deflate(&defstream, Z_FINISH);
deflateEnd(&defstream);

printf("Deflate:\n%lu\n%s\n", strlen(b), b);

// inflate
// zlib struct
z_stream infstream;
infstream.zalloc = Z_NULL;
infstream.zfree = Z_NULL;
infstream.opaque = Z_NULL;
infstream.avail_in = (uInt)sizeof(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

inflateInit(&infstream);
inflate(&infstream, Z_NO_FLUSH);
inflateEnd(&infstream);

printf("Inflate:\n%lu\n%s\n", strlen(c), c);

原文

I am trying to implement the zlib.h deflate and inflate functions to compress and decompress a char array (not a file).

I would like to know if the following syntax is correct ? Am I missing something or defined something incorrectly ?

char a[50] = "Hello World!";
char b[50];
char c[50];

// deflate
// zlib struct
z_stream defstream;
defstream.zalloc = Z_NULL;
defstream.zfree = Z_NULL;
defstream.opaque = Z_NULL;
defstream.avail_in = (uInt)sizeof(a); // size of input
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

deflateInit(&defstream, Z_DEFAULT_COMPRESSION);
deflate(&defstream, Z_FINISH);
deflateEnd(&defstream);

printf("Deflate:\n%lu\n%s\n", strlen(b), b);

// inflate
// zlib struct
z_stream infstream;
infstream.zalloc = Z_NULL;
infstream.zfree = Z_NULL;
infstream.opaque = Z_NULL;
infstream.avail_in = (uInt)sizeof(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

inflateInit(&infstream);
inflate(&infstream, Z_NO_FLUSH);
inflateEnd(&infstream);

printf("Inflate:\n%lu\n%s\n", strlen(c), c);

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近箐 2024-12-13 10:48:42

zlib 已经有一个简单的 inflate/deflate 函数可以使用。

char a[50] = "Hello, world!";
char b[50];
char c[50];

uLong ucompSize = strlen(a)+1; // "Hello, world!" + NULL delimiter.
uLong compSize = compressBound(ucompSize);

// Deflate
compress((Bytef *)b, &compSize, (Bytef *)a, ucompSize);

// Inflate
uncompress((Bytef *)c, &ucompSize, (Bytef *)b, compSize);

如有疑问，请查看 zlib 手册。
我的代码很糟糕，抱歉=/

zlib already has a simple inflate/deflate function you can use.

char a[50] = "Hello, world!";
char b[50];
char c[50];

uLong ucompSize = strlen(a)+1; // "Hello, world!" + NULL delimiter.
uLong compSize = compressBound(ucompSize);

// Deflate
compress((Bytef *)b, &compSize, (Bytef *)a, ucompSize);

// Inflate
uncompress((Bytef *)c, &ucompSize, (Bytef *)b, compSize);

When in doubt, check out the zlib manual.
My code is crappy, sorry =/

回复收藏 0 原文

莳間冲淡了誓言ζ 2024-12-13 10:48:42

你不能像这样 printf 压缩的输出。它不是以 null 终止的。你也不能强求它。

由于您的输入是一个字符串，因此您可能只想传递包括空终止符在内的字符串内容。因此，将avail_in设置为strlen(a) + 1。

在调用deflate后，您需要检查next_out和avail_out字段，以查看有多少数据写入了输出缓冲区。

请参阅此处 deflate 调用下的文档。

这是您修改后的代码。请注意，如果您要压缩的内容不是字符串，则需要更改此设置，并且对于字符串，您可以在不带终止零的情况下进行压缩，并在解压缩后将其添加回来。

char a[50] = "Hello World!";
char b[50];
char c[50];

// deflate
// zlib struct
z_stream defstream;
defstream.zalloc = Z_NULL;
defstream.zfree = Z_NULL;
defstream.opaque = Z_NULL;
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

deflateInit(&defstream, Z_DEFAULT_COMPRESSION);
deflate(&defstream, Z_FINISH);
deflateEnd(&defstream);

// This is one way of getting the size of the output
printf("Deflated size is: %lu\n", (char*)defstream.next_out - b);

// inflate
// zlib struct
z_stream infstream;
infstream.zalloc = Z_NULL;
infstream.zfree = Z_NULL;
infstream.opaque = Z_NULL;
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

inflateInit(&infstream);
inflate(&infstream, Z_NO_FLUSH);
inflateEnd(&infstream);

printf("Inflate:\n%lu\n%s\n", strlen(c), c);

You can't printf the deflated output like this. It's not null terminated. You can't strlen it either.

Since your input is a string though you probably do want to only pass the content of the string including the null terminator. So set avail_in to strlen(a) + 1.

You need to examine the next_out and avail_out fields after you call deflate to see how much data was written to the output buffer.

See documentation here under the deflate call.

Here's your modified code. Note if you're compressing something that is not a string you'll need to change this and also with strings you may compress without the terminating zero and add it back after decompressing.

char a[50] = "Hello World!";
char b[50];
char c[50];

// deflate
// zlib struct
z_stream defstream;
defstream.zalloc = Z_NULL;
defstream.zfree = Z_NULL;
defstream.opaque = Z_NULL;
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

deflateInit(&defstream, Z_DEFAULT_COMPRESSION);
deflate(&defstream, Z_FINISH);
deflateEnd(&defstream);

// This is one way of getting the size of the output
printf("Deflated size is: %lu\n", (char*)defstream.next_out - b);

// inflate
// zlib struct
z_stream infstream;
infstream.zalloc = Z_NULL;
infstream.zfree = Z_NULL;
infstream.opaque = Z_NULL;
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

inflateInit(&infstream);
inflate(&infstream, Z_NO_FLUSH);
inflateEnd(&infstream);

printf("Inflate:\n%lu\n%s\n", strlen(c), c);

回复收藏 0 原文

夏九 2024-12-13 10:48:42

zpipe 示例（http://zlib.net/zpipe.c）几乎涵盖了它，只需删除文件 ops（f 前缀函数），然后替换 in 和 out< /code> 与您的内存缓冲区，尽管仅替换 in 或根据您的使用情况保留缓冲区可能就足够了。请注意，如果您计划拥有未知大小的块，则需要调整 out 缓冲区的大小，以解压缩任意大小的数据