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-rw-r--r--src/shared/util.c62
1 files changed, 62 insertions, 0 deletions
diff --git a/src/shared/util.c b/src/shared/util.c
index 8f6d5e660c..fd54023660 100644
--- a/src/shared/util.c
+++ b/src/shared/util.c
@@ -7931,3 +7931,65 @@ void release_lock_file(LockFile *f) {
f->fd = safe_close(f->fd);
f->operation = 0;
}
+
+static size_t nul_length(const uint8_t *p, size_t sz) {
+ size_t n = 0;
+
+ while (sz > 0) {
+ if (*p != 0)
+ break;
+
+ n++;
+ p++;
+ sz--;
+ }
+
+ return n;
+}
+
+ssize_t sparse_write(int fd, const void *p, size_t sz, size_t run_length) {
+ const uint8_t *q, *w, *e;
+ ssize_t l;
+
+ q = w = p;
+ e = q + sz;
+ while (q < e) {
+ size_t n;
+
+ n = nul_length(q, e - q);
+
+ /* If there are more than the specified run length of
+ * NUL bytes, or if this is the beginning or the end
+ * of the buffer, then seek instead of write */
+ if ((n > run_length) ||
+ (n > 0 && q == p) ||
+ (n > 0 && q + n >= e)) {
+ if (q > w) {
+ l = write(fd, w, q - w);
+ if (l < 0)
+ return -errno;
+ if (l != q -w)
+ return -EIO;
+ }
+
+ if (lseek(fd, n, SEEK_CUR) == (off_t) -1)
+ return -errno;
+
+ q += n;
+ w = q;
+ } else if (n > 0)
+ q += n;
+ else
+ q ++;
+ }
+
+ if (q > w) {
+ l = write(fd, w, q - w);
+ if (l < 0)
+ return -errno;
+ if (l != q - w)
+ return -EIO;
+ }
+
+ return q - (const uint8_t*) p;
+}