compat/mmap.c

   1 #include <stdio.h>
   2 #include <stdlib.h>
   3 #include <unistd.h>
   4 #include <errno.h>
   5 #include "../cache.h"
   6
   7 typedef struct fakemmapwritable {
   8         void *start;
   9         size_t length;
  10         int fd;
  11         off_t offset;
  12         struct fakemmapwritable *next;
  13 } fakemmapwritable;
  14
  15 static fakemmapwritable *writablelist = NULL;
  16
  17 void *gitfakemmap(void *start, size_t length, int prot , int flags, int fd, off_t offset)
  18 {
  19         int n = 0;
  20
  21         if(start != NULL)
  22                 die("Invalid usage of gitfakemmap.");
  23
  24         if(lseek(fd, offset, SEEK_SET)<0) {
  25                 errno = EINVAL;
  26                 return MAP_FAILED;
  27         }
  28
  29         start = xmalloc(length);
  30         if(start == NULL) {
  31                 errno = ENOMEM;
  32                 return MAP_FAILED;
  33         }
  34
  35         while(n < length) {
  36                 int count = read(fd, start+n, length-n);
  37
  38                 if(count == 0) {
  39                         memset(start+n, 0, length-n);
  40                         break;
  41                 }
  42
  43                 if(count < 0) {
  44                         free(start);
  45                         errno = EACCES;
  46                         return MAP_FAILED;
  47                 }
  48
  49                 n += count;
  50         }
  51
  52         if(prot & PROT_WRITE) {
  53                 fakemmapwritable *next = xmalloc(sizeof(fakemmapwritable));
  54                 next->start = start;
  55                 next->length = length;
  56                 next->fd = dup(fd);
  57                 next->offset = offset;
  58                 next->next = writablelist;
  59                 writablelist = next;
  60         }
  61
  62         return start;
  63 }
  64
  65 int gitfakemunmap(void *start, size_t length)
  66 {
  67         fakemmapwritable *writable = writablelist, *before = NULL;
  68
  69         while(writable && (writable->start > start + length
  70                         || writable->start + writable->length < start)) {
  71                 before = writable;
  72                 writable = writable->next;
  73         }
  74
  75         if(writable) {
  76                 /* need to write back the contents */
  77                 int n = 0;
  78
  79                 if(writable->start != start || writable->length != length)
  80                         die("fakemmap does not support partial write back.");
  81
  82                 if(lseek(writable->fd, writable->offset, SEEK_SET) < 0) {
  83                         free(start);
  84                         errno = EBADF;
  85                         return -1;
  86                 }
  87
  88                 while(n < length) {
  89                         int count = write(writable->fd, start + n, length - n);
  90
  91                         if(count < 0) {
  92                                 errno = EINVAL;
  93                                 return -1;
  94                         }
  95
  96                         n += count;
  97                 }
  98
  99                 close(writable->fd);
 100
 101                 if(before)
 102                         before->next = writable->next;
 103                 else
 104                         writablelist = writable->next;
 105
 106                 free(writable);
 107         }
 108
 109         free(start);
 110
 111         return 0;
 112 }
 113