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Copyright (C) 2015 Francesc Alted
License: MIT (see LICENSE.txt)
Example program demonstrating use of the Blosc filter using the Windows Run-Time Dynamic Linking technique:
This allows to link your app in run-time with DLLs made with different compatible compilers
(e.g. VS2013 and mingw-w64).
To compile this program (be aware that you should match your compiler 32-bit/64-bit with your DLL):
cl /Ox /Fewin-dynamic-linking.exe /I..\blosc win-dynamic-linking.c
To run:
$ win-dynamic-linking.exe
Blosc version info:
Compression: 400000000 -> 19928862 (20.1x)
Decompression succesful!
Succesful roundtrip!
#include <stdio.h>
#include <blosc.h>
#include <windows.h>
#define SIZE 100*1000*1000
#define SHAPE {100,1000,1000}
#define CHUNKSHAPE {1,1000,1000}
/* Definition for the compression and decompression blosc routines */
typedef int (__cdecl *COMPRESS_CTX)(int clevel, int doshuffle, size_t typesize,
size_t nbytes, const void* src, void* dest,
size_t destsize, const char* compressor,
size_t blocksize, int numinternalthreads);
typedef int (__cdecl *DECOMPRESS_CTX)(const void *src, void *dest,
size_t destsize, int numinternalthreads);
typedef char* (__cdecl *GET_VERSION_STRING)(void);
int main(){
HINSTANCE BDLL; /* Handle to DLL */
COMPRESS_CTX blosc_compress_ctx; /* Function pointer for compression */
DECOMPRESS_CTX blosc_decompress_ctx; /* Function pointer for decompression */
GET_VERSION_STRING blosc_get_version_string;
static float data[SIZE];
static float data_out[SIZE];
static float data_dest[SIZE];
int isize = SIZE*sizeof(float), osize = SIZE*sizeof(float);
int dsize = SIZE*sizeof(float), csize;
int i;
BDLL = LoadLibrary(TEXT("myblosc.dll"));
if (BDLL == NULL) {
printf("Cannot find myblosc.dll library!\n");
goto out;
blosc_compress_ctx = (COMPRESS_CTX)GetProcAddress(BDLL, "blosc_compress_ctx");
if (!blosc_compress_ctx) {
// handle the error
printf("Cannot find blosc_compress_ctx() function!\n");
goto out;
blosc_decompress_ctx = (DECOMPRESS_CTX)GetProcAddress(BDLL, "blosc_decompress_ctx");
if (!blosc_decompress_ctx) {
// handle the error
printf("Cannot find blosc_decompress_ctx() function!\n");
goto out;
blosc_get_version_string = (GET_VERSION_STRING)GetProcAddress(BDLL, "blosc_get_version_string");
if (!blosc_get_version_string) {
// handle the error
printf("Cannot find blosc_get_version_string() function!\n");
goto out;
for(i=0; i<SIZE; i++){
data[i] = i;
/* Register the filter with the library */
printf("Blosc version info: %s\n", blosc_get_version_string());
/* Compress with clevel=3, shuffle active, 16-bytes data size, blosclz and 2 threads */
csize = blosc_compress_ctx(3, 1, 16, isize, data, data_out, osize, "blosclz", 0, 2);
if (csize == 0) {
printf("Buffer is uncompressible. Giving up.\n");
return 1;
else if (csize < 0) {
printf("Compression error. Error code: %d\n", csize);
return csize;
printf("Compression: %d -> %d (%.1fx)\n", isize, csize, (1.*isize) / csize);
/* Decompress */
dsize = blosc_decompress_ctx(data_out, data_dest, dsize, 1);
if (dsize < 0) {
printf("Decompression error. Error code: %d\n", dsize);
return dsize;
printf("Decompression succesful!\n");
if(data[i] != data_dest[i]) {
printf("Decompressed data differs from original!\n");
return -1;
printf("Succesful roundtrip!\n");
return 0;
return -1;