MemGrow.c

   1 #include "MemGrow.h"
   2 #include <string.h>
   3 #include <stdlib.h>
   4 #include <limits.h>
   5 #include <fcntl.h>
   6 #include <unistd.h>
   7 #ifndef PAGE_SIZE
   8 #define PAGE_SIZE 4096
   9 #endif
  10
  11 void mem_init(MG* mem) {
  12         memset(mem, 0, sizeof *mem);
  13 }
  14
  15 void mem_free(MG* mem) {
  16         if(mem->mem) free(mem->mem);
  17         mem_init(mem);
  18 }
  19
  20 /* returns 1 if realloc was necessary, -1 if no realloc was necessary, 0 when realloc failed */
  21 int mem_grow_if_needed(MG *mem, size_t newsize) {
  22         if(newsize > mem->capa) {
  23                 size_t nucap = mem->capa * 2;
  24                 if(newsize > nucap) {
  25                         nucap = newsize;
  26                         if(nucap & (PAGE_SIZE -1)) {
  27                                 nucap += PAGE_SIZE;
  28                                 nucap &= ~(PAGE_SIZE -1);
  29                         }
  30                 }
  31                 void *nu = realloc(mem->mem, nucap);
  32                 if(!nu) return 0;
  33                 mem->mem = nu;
  34                 mem->capa = nucap;
  35                 return 1;
  36         }
  37         return -1;
  38 }
  39
  40 int mem_write(MG *mem, size_t offset, void* data, size_t size) {
  41         int ret;
  42         size_t needed = offset + size;
  43         if(needed < offset) return 0; /* overflow */
  44         if((ret = mem_grow_if_needed(mem, needed))) {
  45                 memcpy((char*) mem->mem + offset, data, size);
  46                 if(needed > mem->used) mem->used = needed;
  47         }
  48         return ret;
  49 }
  50
  51 int mem_append(MG *mem, void* data, size_t size) {
  52         return mem_write(mem, mem->used, data, size);
  53 }
  54
  55 void* mem_getptr(MG* mem, size_t offset, size_t byteswanted) {
  56         if(!mem->mem || offset + byteswanted > mem->used) return 0;
  57         return (char*)mem->mem + offset;
  58 }
  59
  60 void mem_set(MG* mem, void* data, size_t used, size_t allocated) {
  61         mem->mem = data;
  62         mem->used = used;
  63         mem->capa = allocated;
  64 }
  65
  66 int mem_write_stream(MG* mem, FILE* out) {
  67         if(!mem->mem || !mem->used) return 0;
  68         int ret = (fwrite(mem->mem, 1, mem->used, out) == mem->used);
  69         return ret;
  70 }
  71
  72 int mem_write_file(MG* mem, char* fn) {
  73         FILE *out = fopen(fn, "wb");
  74         if(!out) return 0;
  75         int ret = mem_write_stream(mem, out);
  76         fclose(out);
  77         return ret;
  78 }