From d894fe2e0d3bc2d3d9d3a2b84d372fb2ea2b5ca0 Mon Sep 17 00:00:00 2001
From: Martin Mares <mj@ucw.cz>
Date: Sat, 10 Mar 2007 20:15:06 +0100
Subject: [PATCH] Fastbufs now work better on unseekable files.

The seek callback returns success, bseek() and bsetpos() dies if seek
fails, bfilesize() returns -1 if the file is unseekable.
---
 lib/fastbuf.c   | 10 +++++++---
 lib/fastbuf.h   |  4 ++--
 lib/fb-buffer.c |  3 ++-
 lib/fb-file.c   |  7 ++++---
 lib/fb-grow.c   |  3 ++-
 lib/fb-mem.c    |  6 +++---
 lib/fb-mmap.c   |  3 ++-
 7 files changed, 22 insertions(+), 14 deletions(-)

diff --git a/lib/fastbuf.c b/lib/fastbuf.c
index 980d53aa..79229d4e 100644
--- a/lib/fastbuf.c
+++ b/lib/fastbuf.c
@@ -38,7 +38,8 @@ inline void bsetpos(struct fastbuf *f, sh_off_t pos)
   else
     {
       bflush(f);
-      f->seek(f, pos, SEEK_SET);
+      if (!f->seek || !f->seek(f, pos, SEEK_SET))
+	die("bsetpos: stream not seekable");
     }
 }
 
@@ -52,7 +53,8 @@ void bseek(struct fastbuf *f, sh_off_t pos, int whence)
       return bsetpos(f, btell(f) + pos);
     case SEEK_END:
       bflush(f);
-      f->seek(f, pos, SEEK_END);
+      if (!f->seek || !f->seek(f, pos, SEEK_END))
+	die("bseek: stream not seekable");
       break;
     default:
       die("bseek: invalid whence=%d", whence);
@@ -192,7 +194,9 @@ bfilesize(struct fastbuf *f)
   if (!f)
     return 0;
   sh_off_t pos = btell(f);
-  bseek(f, 0, SEEK_END);
+  bflush(f);
+  if (!f->seek(f, pos, SEEK_END))
+    return -1;
   sh_off_t len = btell(f);
   bsetpos(f, pos);
   return len;
diff --git a/lib/fastbuf.h b/lib/fastbuf.h
index 598a21d9..12bb5da2 100644
--- a/lib/fastbuf.h
+++ b/lib/fastbuf.h
@@ -73,7 +73,7 @@ struct fastbuf {
   sh_off_t pos;				/* Position of bstop in the file */
   int (*refill)(struct fastbuf *);	/* Get a buffer with new data */
   void (*spout)(struct fastbuf *);	/* Write buffer data to the file */
-  void (*seek)(struct fastbuf *, sh_off_t, int);  /* Slow path for bseek(), buffer already flushed */
+  int (*seek)(struct fastbuf *, sh_off_t, int);  /* Slow path for bseek(), buffer already flushed; returns success */
   void (*close)(struct fastbuf *);	/* Close the stream */
   int (*config)(struct fastbuf *, uns, int);	/* Configure the stream */
   int can_overwrite_buffer;		/* Can the buffer be altered? (see discussion above) 0=never, 1=temporarily, 2=permanently */
@@ -153,7 +153,7 @@ void bflush(struct fastbuf *f);
 void bseek(struct fastbuf *f, sh_off_t pos, int whence);
 void bsetpos(struct fastbuf *f, sh_off_t pos);
 void brewind(struct fastbuf *f);
-sh_off_t bfilesize(struct fastbuf *f);
+sh_off_t bfilesize(struct fastbuf *f);		// -1 if not seekable
 
 static inline sh_off_t btell(struct fastbuf *f)
 {
diff --git a/lib/fb-buffer.c b/lib/fb-buffer.c
index 09c74293..9ad248a2 100644
--- a/lib/fb-buffer.c
+++ b/lib/fb-buffer.c
@@ -18,7 +18,7 @@ fbbuf_refill(struct fastbuf *f UNUSED)
   return 0;
 }
 
-static void
+static int
 fbbuf_seek(struct fastbuf *f, sh_off_t pos, int whence)
 {
   /* Somebody might want to seek to the end of buffer, try to be nice to him. */
@@ -29,6 +29,7 @@ fbbuf_seek(struct fastbuf *f, sh_off_t pos, int whence)
   f->bptr = f->buffer + pos;
   f->bstop = f->bufend;
   f->pos = len;
+  return 1;
 }
 
 void
diff --git a/lib/fb-file.c b/lib/fb-file.c
index 0dcf22a9..c4543277 100644
--- a/lib/fb-file.c
+++ b/lib/fb-file.c
@@ -53,16 +53,17 @@ bfd_spout(struct fastbuf *f)
   f->bptr = f->buffer = FB_BUFFER(f);
 }
 
-static void
+static int
 bfd_seek(struct fastbuf *f, sh_off_t pos, int whence)
 {
   if (whence == SEEK_SET && pos == f->pos)
-    return;
+    return 1;
 
   sh_off_t l = sh_seek(FB_FILE(f)->fd, pos, whence);
   if (l < 0)
-    die("lseek on %s: %m", f->name);
+    return 0;
   f->pos = l;
+  return 1;
 }
 
 static void
diff --git a/lib/fb-grow.c b/lib/fb-grow.c
index 0b04817f..1a10a501 100644
--- a/lib/fb-grow.c
+++ b/lib/fb-grow.c
@@ -45,7 +45,7 @@ fbgrow_spout(struct fastbuf *b)
     }
 }
 
-static void
+static int
 fbgrow_seek(struct fastbuf *b, sh_off_t pos, int whence)
 {
   ASSERT(FB_GBUF(b)->last_written);	/* Seeks allowed only in read mode */
@@ -56,6 +56,7 @@ fbgrow_seek(struct fastbuf *b, sh_off_t pos, int whence)
   b->bptr = b->buffer + pos;
   b->bstop = FB_GBUF(b)->last_written;
   b->pos = len;
+  return 1;
 }
 
 static void
diff --git a/lib/fb-mem.c b/lib/fb-mem.c
index 0de590e0..c3f104f1 100644
--- a/lib/fb-mem.c
+++ b/lib/fb-mem.c
@@ -93,7 +93,7 @@ fbmem_spout(struct fastbuf *f)
   FB_MEM(f)->block = bb;
 }
 
-static void
+static int
 fbmem_seek(struct fastbuf *f, sh_off_t pos, int whence)
 {
   struct memstream *m = FB_MEM(f)->stream;
@@ -115,7 +115,7 @@ fbmem_seek(struct fastbuf *f, sh_off_t pos, int whence)
 	  f->bufend = f->bstop = b->data + b->size;
 	  f->pos = b->pos + b->size;
 	  FB_MEM(f)->block = b;
-	  return;
+	  return 1;
 	}
     }
   if (!m->first && !pos)
@@ -124,7 +124,7 @@ fbmem_seek(struct fastbuf *f, sh_off_t pos, int whence)
       f->buffer = f->bptr = f->bufend = NULL;
       f->pos = 0;
       FB_MEM(f)->block = NULL;
-      return;
+      return 1;
     }
   die("fbmem_seek to invalid offset");
 }
diff --git a/lib/fb-mmap.c b/lib/fb-mmap.c
index 85dc27ee..41e65832 100644
--- a/lib/fb-mmap.c
+++ b/lib/fb-mmap.c
@@ -117,7 +117,7 @@ bfmm_spout(struct fastbuf *f)
   DBG(" -> %p %p %p(%x) %p", f->buffer, f->bptr, f->bstop, (int)f->pos, f->bufend);
 }
 
-static void
+static int
 bfmm_seek(struct fastbuf *f, sh_off_t pos, int whence)
 {
   if (whence == SEEK_END)
@@ -128,6 +128,7 @@ bfmm_seek(struct fastbuf *f, sh_off_t pos, int whence)
   f->pos = pos;
   f->bptr = f->bstop = f->bufend;	/* force refill/spout call */
   DBG("Seek -> %p %p %p(%x) %p", f->buffer, f->bptr, f->bstop, (int)f->pos, f->bufend);
+  return 1;
 }
 
 static void
-- 
2.39.2