From b144af9a1a50583d9177ea4d2b0f94eee4178f84 Mon Sep 17 00:00:00 2001
From: Nick Bowler <draconx@gmail.com>
Date: Sat, 22 Dec 2007 23:11:26 -0500
Subject: [PATCH] Fix lbx_extract's seeking to maintain a correct offset even
 on errors.

---
 src/lbx.c     | 66 +++++++++++++++++++++++++--------------------------
 src/lbxtool.c |  1 +
 2 files changed, 34 insertions(+), 33 deletions(-)

diff --git a/src/lbx.c b/src/lbx.c
index 3eac708..597d043 100644
--- a/src/lbx.c
+++ b/src/lbx.c
@@ -106,26 +106,40 @@ int lbx_stat(struct lbx_state *lbx, size_t index, struct lbx_statbuf *buf)
 	return 0;
 }
 
-/*
- * Read and discard len bytes from the file.  On success, returns 0.  On
- * failure, returns -1 and sets lbx_errno.
- */
-static int skipdata(FILE *f, size_t len)
+/* Advance to the beginning of the index'th file by either fseek or reading. */
+static int _lbx_fseek(struct lbx_state *lbx, size_t base)
 {
-	unsigned char buf[1024];
-	
-	while (len) {
-		if (fread(buf, MIN(sizeof buf, len), 1, f) != 1) {
-			if (feof(f)) {
-				lbx_errno = LBX_EEOF;
-			} else {
-				lbx_errno = -errno;
+	static unsigned char oblivion[1024];
+	long dist;
+
+	if (lbx->foff < base) {
+		dist = base - lbx->foff;
+	} else if (lbx->foff > base) {
+		dist = -(long)(lbx->foff - base);
+	} else {
+		return 0;
+	}
+
+	if (fseek(lbx->f, dist, SEEK_CUR) == 0) {
+		lbx->foff += dist;
+	} else if (lbx->foff < base) {
+		while (dist) {
+			size_t rc, amt = MIN(sizeof oblivion, dist);
+			rc = fread(oblivion, 1, amt, lbx->f);
+			lbx->foff += rc;
+			dist -= rc;
+			if (rc < amt) {
+				if (feof(lbx->f))
+					lbx_errno = LBX_EEOF;
+				else
+					lbx_errno = -errno;
+				return -1;
 			}
-			return -1;
 		}
-		len -= MIN(sizeof buf, len);
+	} else {
+		lbx_errno = -errno;
+		return -1;
 	}
-
 	return 0;
 }
 
@@ -142,23 +156,9 @@ size_t lbx_extract(struct lbx_state *lbx, size_t index, FILE *of)
 	base = lbx->offsets[index];
 	len  = lbx->offsets[index+1] - lbx->offsets[index];
 
-	/* Seek to the beginning of the file. */
-	if (lbx->foff != base) {
-		int seekrc;
-		long dist = (lbx->foff < base) ?  (base - lbx->foff)
-		                               : -(lbx->foff - base);
-
-		seekrc = fseek(lbx->f, dist, SEEK_CUR);
-		if (seekrc == -1 && lbx->foff < base) {
-			if (skipdata(lbx->f, dist) == -1) {
-				/* lbx_errno set by skipdata */
-				return 0;
-			}
-		} else if (seekrc == -1) {
-			lbx_errno = -errno;
-			return 0;
-		}
-		lbx->foff += dist; /* FIXME: failed skipdata breaks this. */
+	if (_lbx_fseek(lbx, base) == -1) {
+		/* lbx_errno set by _lbx_fseek(). */
+		return 0;
 	}
 
 	/* Copy file data */
diff --git a/src/lbxtool.c b/src/lbxtool.c
index a220cea..5435d5f 100644
--- a/src/lbxtool.c
+++ b/src/lbxtool.c
@@ -81,6 +81,7 @@ int extract(FILE *f, const char *name, int verbose) {
 		if (verbose) printf("extracting %s...\n", stat.name);
 		rc = lbx_extract(lbx, i, of);
 		if (rc < stat.size) {
+			if (rc == 0) remove(stat.name);
 			errmsg("error extracting %s: %s.\n",
 			       stat.name, lbx_strerror());
 			break;
-- 
2.43.2