From aaa66176662ab9d45e16702e282274c4b8c2a075 Mon Sep 17 00:00:00 2001
From: Daniel Erat <dan@erat.org>
Date: Tue, 19 Jul 2011 22:24:58 +0000
Subject: [PATCH] sqlite: make read match behavior of unix vfs

Change-Id: Ibcae7ee7f989ad535b00df87a2fa03316f3dad01
---
 misc/sqlite/sqlite3_os_go.c |  4 +---
 misc/sqlite/vfs.go          | 19 +++++++++++--------
 2 files changed, 12 insertions(+), 11 deletions(-)

diff --git a/misc/sqlite/sqlite3_os_go.c b/misc/sqlite/sqlite3_os_go.c
index 5bb16b528..ddd0710cd 100644
--- a/misc/sqlite/sqlite3_os_go.c
+++ b/misc/sqlite/sqlite3_os_go.c
@@ -24,9 +24,7 @@ static int go_file_close(sqlite3_file* file) {
 }
 
 static int go_file_read(sqlite3_file* file, void* dest, int iAmt, sqlite3_int64 iOfst) {
-  return GoFileRead(((GoFile*) file)->fd, dest, iAmt, iOfst) == 0 ?
-      SQLITE_OK :
-      SQLITE_ERROR;
+  return GoFileRead(((GoFile*) file)->fd, dest, iAmt, iOfst);
 }
 
 static int go_file_write(sqlite3_file* file, const void* src, int iAmt, sqlite3_int64 iOfst) {
diff --git a/misc/sqlite/vfs.go b/misc/sqlite/vfs.go
index c1334870d..c1b7c0979 100644
--- a/misc/sqlite/vfs.go
+++ b/misc/sqlite/vfs.go
@@ -34,7 +34,10 @@ func GoFileClose(fd C.int) (int) {
 }
 
 //export GoFileRead
-// Returns 0 on success and -1 on error.
+// Returns SQLite error codes to be returned by xRead:
+//   SQLITE_OK: read n bytes
+//   SQLITE_IOERR_READ: got error while reading
+//   SQLITE_IOERR_SHORT_READ: read fewer than n bytes; rest will be zeroed
 func GoFileRead(fd C.int, dst *C.char, n C.int, offset C.long) (rv int) {
 	println("reading", n, "bytes at offset", offset, "from fd", fd);
 	defer func() {
@@ -43,7 +46,7 @@ func GoFileRead(fd C.int, dst *C.char, n C.int, offset C.long) (rv int) {
 
 	file := GetFile(int(fd))
 	if file == nil {
-		return -1
+		return C.SQLITE_IOERR_READ
 	}
 
 	buf := make([]byte, n)
@@ -56,16 +59,16 @@ func GoFileRead(fd C.int, dst *C.char, n C.int, offset C.long) (rv int) {
 			break
 		}
 		if err != nil {
-			return -1
+			return C.SQLITE_IOERR_READ
 		}
 	}
 
-	if n != 0 {
-		return -1
-	}
-
 	C.memcpy(unsafe.Pointer(dst), unsafe.Pointer(&buf[0]), C.size_t(len(buf)))
-	return 0
+
+	if n != 0 {
+		return C.SQLITE_IOERR_SHORT_READ
+	}
+	return C.SQLITE_OK
 }
 
 //export GoFileFileSize