Fix `distcheck' complaints.

[disorder] / common / hreader.c

diff --git a/common/hreader.c b/common/hreader.c
new file mode 100644 (file)
index 0000000..bdf3c07
--- /dev/null
+++ b/common/hreader.c
@@ -0,0 +1,114 @@
+/*
+ * This file is part of DisOrder
+ * Copyright (C) 2010 Richard Kettlewell
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ * 
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+/** @file lib/hreader.c
+ * @brief Hands-off reader - read files without keeping them open
+ */
+#include <config.h>
+#include "hreader.h"
+#include "mem.h"
+#include <string.h>
+#include <fcntl.h>
+#include <sys/stat.h>
+#include <errno.h>
+#include <unistd.h>
+
+static int hreader_fill(struct hreader *h, off_t offset);
+
+int hreader_init(const char *path, struct hreader *h) {
+  struct stat sb;
+  if(stat(path, &sb) < 0)
+    return -1;
+  memset(h, 0, sizeof *h);
+  h->path = xstrdup(path);
+  h->size = sb.st_size;
+  h->bufsize = 65536;
+  h->buffer = xmalloc_noptr(h->bufsize);
+  return 0;
+}
+
+void hreader_close(struct hreader *h) {
+  xfree(h->path);
+  xfree(h->buffer);
+}
+
+int hreader_read(struct hreader *h, void *buffer, size_t n) {
+  int r = hreader_pread(h, buffer, n, h->read_offset);
+  if(r > 0)
+    h->read_offset += r;
+  return r;
+}
+
+int hreader_pread(struct hreader *h, void *buffer, size_t n, off_t offset) {
+  size_t bytes_read = 0;
+
+  while(bytes_read < n) {
+    // If the desired byte range is outside the file, fetch new contents
+    if(offset < h->buf_offset || offset >= h->buf_offset + (off_t)h->bytes) {
+      int r = hreader_fill(h, offset);
+      if(r < 0)
+        return -1;                      /* disaster! */
+      else if(r == 0)
+        break;                          /* end of file */
+    }
+    // Figure out how much we can read this time round
+    size_t left = h->bytes - (offset - h->buf_offset);
+    // Truncate the read if we don't want that much
+    if(left > (n - bytes_read))
+      left = n - bytes_read;
+    memcpy((char *)buffer + bytes_read,
+           h->buffer + (offset - h->buf_offset),
+           left);
+    offset += left;
+    bytes_read += left;
+  }
+  return bytes_read;
+}
+
+static int hreader_fill(struct hreader *h, off_t offset) {
+  int fd = open(h->path, O_RDONLY);
+  if(fd < 0)
+    return -1;
+  int n = pread(fd, h->buffer, h->bufsize, offset);
+  close(fd);
+  if(n < 0)
+    return -1;
+  h->buf_offset = offset;
+  h->bytes = n;
+  return n;
+}
+
+off_t hreader_seek(struct hreader *h, off_t offset, int whence) {
+  switch(whence) {
+  case SEEK_SET: break;
+  case SEEK_CUR: offset += h->read_offset; break;
+  case SEEK_END: offset += h->size; break;
+  default: einval: errno = EINVAL; return -1;
+  }
+  if(offset < 0) goto einval;
+  h->read_offset = offset;
+  return offset;
+}
+
+/*
+Local Variables:
+c-basic-offset:2
+comment-column:40
+fill-column:79
+indent-tabs-mode:nil
+End:
+*/