read into a struct - BlitzCoder.net

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Socoder -> C/C++/C#/Other -> read into a struct
Tue, 28 Apr 2009, 20:32
cthug	How do you read (from memory), into a structure in c (not c++). do you do something like: struct tarHeader; int i; char[512] c; for(i = 0; i != 512; i++) { c[i] = memory[i]; } &tarHeader = &c; --v as you may have noticed i am reading TAR archives, I want to store the TAR header in a struct which is before each file in the archive and see if it is the correct filename. Well then copy the contents. Thanks -=-=- CTHUG.co.nr Get Ubuntu
Tue, 28 Apr 2009, 20:58
Cower	Something like this? typedef struct s_tarHeader { char filename[100]; char mode[8]; char uid[8]; char gid[8]; char size[12]; char mtime[12]; char chksum[8]; char link; char linkname[100]; char magic[6]; char version[2]; char uname[32]; char gname[32]; char devmajor[8]; char devminor[8]; char prefix[155]; char _unused[12]; } tarHeader_t; int main( int argc, char ** argv ) { tarHeader_t header; if ( argv < 2 ) { fread(&header, sizeof(&header), 1, stdin); } else { FILE *tarFile = NULL; for (int arg = 1; i < argc; ++i) { if ( tarFile = fopen(argv[arg], "rb") ) { if ( fread(&header, sizeof(tarHeader_t), 1, tarFile) != sizeof(tarHeader_t) ) { fprintf(stderr, "Failed to read header from '%s'\n", argv[arg]); } fclose(tarFile); } else { fprintf(stderr, "Failed to open '%s' for reading\n", argv[arg]) } } } } --v For something more advanced, you could look into using mmap to map the file into the process's memory. However, I'm not sure if mmap works under Windows, and there are important differences in how it works between operating systems.
Tue, 28 Apr 2009, 21:04
cthug	That seems the way to do it, btw I am using USTAR (GNU TAR), format. . Oh and this will be cross platform, cuz I am using SDL and openGL, so no OS specific stuff like memory map Thanks -=-=- CTHUG.co.nr Get Ubuntu
Tue, 28 Apr 2009, 21:24
Cower	Well, that includes the USTAR header, so just check your tar files for the "ustar" magic string and you should be fine.