+static char abuf[4096+4096];
+static int aread(int fd, void *buf, int len)
+{
+ /* aligned read.
+ * On devices with a 4K sector size, we need to read
+ * the full sector and copy relevant bits into
+ * the buffer
+ */
+ int bsize;
+ char *b;
+ int n;
+ if (ioctl(fd, BLKSSZGET, &bsize) != 0 ||
+ bsize <= len)
+ return read(fd, buf, len);
+ if (bsize > 4096)
+ return -1;
+ b = (char*)(((long)(abuf+4096))&~4095UL);
+
+ n = read(fd, b, bsize);
+ if (n <= 0)
+ return n;
+ lseek(fd, len - n, 1);
+ if (n > len)
+ n = len;
+ memcpy(buf, b, n);
+ return n;
+}
+
+static int awrite(int fd, void *buf, int len)
+{
+ /* aligned write.
+ * On devices with a 4K sector size, we need to write
+ * the full sector. We pre-read if the sector is larger
+ * than the write.
+ * The address must be sector-aligned.
+ */
+ int bsize;
+ char *b;
+ int n;
+ if (ioctl(fd, BLKSSZGET, &bsize) != 0 ||
+ bsize <= len)
+ return write(fd, buf, len);
+ if (bsize > 4096)
+ return -1;
+ b = (char*)(((long)(abuf+4096))&~4095UL);
+
+ n = read(fd, b, bsize);
+ if (n <= 0)
+ return n;
+ lseek(fd, -n, 1);
+ memcpy(b, buf, len);
+ n = write(fd, b, bsize);
+ if (n <= 0)
+ return n;
+ lseek(fd, len - n, 1);
+ return len;
+}
+