CODEWITHSUNDEEP
c++embeddedzlib
Pnzy
Pnzy

Reputation: 25

ZLIB with small memory usage

I'm working on embedded device (STM32) with < 5kb free FLASH memory left. I'm trying to compress string with zlib library. I created function HERE and it returns -2 (Z_STREAM_ERROR).

What I did:

Then I found this On deflate.c which I cannot lower MAX_WBITS less than 8:

if (memLevel < 1 || memLevel > MAX_MEM_LEVEL || method != Z_DEFLATED ||
        windowBits < 8 || windowBits > 15 || level < 0 || level > 9 ||
        strategy < 0 || strategy > Z_FIXED || (windowBits == 8 && wrap != 1)) {
        return Z_STREAM_ERROR;
}
if (windowBits == 8) windowBits = 9;  /* until 256-byte window bug fixed */

Then I set it to MAX_MEM_LEVEL to 1 and MAX_WBITS to 8 but when I try to compile it always returns region FLASH overflowed by 15960 bytes. Looks like I run out of memory.

Then I tried another example:

Result still the same, region FLASH overflowed by 15960 bytes. Is there any other way to do it with FLASH memory only 5kb left?

Note:

Upvotes: 0

Views: 984

Answers (1)

Mark Adler
Mark Adler

Reputation: 112422

No. The minimum amount of RAM required by deflate is 9K. You might try a different compressor, such as lz4.

The deflate code itself compiles to 33K on my machine (x86_64 ISA), with speed optimization. I tried compiling with aggressive space optimization, which got it down to 25K.

Upvotes: 1

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