[PATCH] If NO_MMAP is defined, fake mmap() and munmap()

[git.git] / compat / mmap.c

diff --git a/compat/mmap.c b/compat/mmap.c
new file mode 100644 (file)
index 0000000..fca6321
--- /dev/null
+++ b/compat/mmap.c
@@ -0,0 +1,113 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <errno.h>
+#include "../cache.h"
+
+typedef struct fakemmapwritable {
+       void *start;
+       size_t length;
+       int fd;
+       off_t offset;
+       struct fakemmapwritable *next;
+} fakemmapwritable;
+
+static fakemmapwritable *writablelist = NULL;
+
+void *gitfakemmap(void *start, size_t length, int prot , int flags, int fd, off_t offset)
+{
+       int n = 0;
+
+       if(start != NULL)
+               die("Invalid usage of gitfakemmap.");
+
+       if(lseek(fd, offset, SEEK_SET)<0) {
+               errno = EINVAL;
+               return MAP_FAILED;
+       }
+
+       start = xmalloc(length);
+       if(start == NULL) {
+               errno = ENOMEM;
+               return MAP_FAILED;
+       }
+
+       while(n < length) {
+               int count = read(fd, start+n, length-n);
+
+               if(count == 0) {
+                       memset(start+n, 0, length-n);
+                       break;
+               }
+
+               if(count < 0) {
+                       free(start);
+                       errno = EACCES;
+                       return MAP_FAILED;
+               }
+
+               n += count;
+       }
+
+       if(prot & PROT_WRITE) {
+               fakemmapwritable *next = xmalloc(sizeof(fakemmapwritable));
+               next->start = start;
+               next->length = length;
+               next->fd = dup(fd);
+               next->offset = offset;
+               next->next = writablelist;
+               writablelist = next;
+       }
+
+       return start;
+}
+
+int gitfakemunmap(void *start, size_t length)
+{
+       fakemmapwritable *writable = writablelist, *before = NULL;
+
+       while(writable && (writable->start > start + length
+                       || writable->start + writable->length < start)) {
+               before = writable;
+               writable = writable->next;
+       }
+
+       if(writable) {
+               /* need to write back the contents */
+               int n = 0;
+
+               if(writable->start != start || writable->length != length)
+                       die("fakemmap does not support partial write back.");
+
+               if(lseek(writable->fd, writable->offset, SEEK_SET) < 0) {
+                       free(start);
+                       errno = EBADF;
+                       return -1;
+               }
+
+               while(n < length) {
+                       int count = write(writable->fd, start + n, length - n);
+
+                       if(count < 0) {
+                               errno = EINVAL;
+                               return -1;
+                       }
+
+                       n += count;
+               }
+
+               close(writable->fd);
+
+               if(before)
+                       before->next = writable->next;
+               else
+                       writablelist = writable->next;
+
+               free(writable);
+       }
+
+       free(start);
+
+       return 0;
+}
+