When writing, the data needn't start at the beginning of the buffer.

[libucw.git] / lib / fastbuf.h

diff --git a/lib/fastbuf.h b/lib/fastbuf.h
index 69df9b710bc4f565a38c85b65143fdf7f84dba41..1f502ce5d733a7ac85d95e7abbd20be2446a1a02 100644 (file)
--- a/lib/fastbuf.h
+++ b/lib/fastbuf.h
@@ -1,7 +1,7 @@
 /*
  *     Sherlock Library -- Fast Buffered I/O
  *
- *     (c) 1997--2000 Martin Mares <mj@ucw.cz>
+ *     (c) 1997--2002 Martin Mares <mj@ucw.cz>
  *
  *     This software may be freely distributed and used according to the terms
  *     of the GNU Lesser General Public License.
@@ -19,7 +19,8 @@
 #include "lib/unaligned.h"
 
 /*
- *  Generic buffered I/O on a top of buffer swapping functions.
+ *  Generic buffered I/O. You supply hooks to be called for low-level operations
+ *  (swapping of buffers, seeking and closing), we do the rest.
  *
  *  Buffer layout when reading:
  *
@@ -35,24 +36,28 @@
  *
  *  When writing:
  *
- *  +----------------+---------------------------+
- *  | written data   | free space                |
- *  +----------------+---------------------------+
- *  ^                 ^                           ^
- *  buffer=bstop      bptr                        bufend
+ *  +--------+--------------+--------------------+
+ *  | unused | written data | free space         |
+ *  +--------+--------------+--------------------+
+ *  ^         ^              ^                    ^
+ *  buffer    bstop          bptr                 bufend
+ *
+ *  Dirty tricks:
+ *
+ *    - You can mix reads and writes on the same stream, but you must
+ *     call bflush() in between and remember that the file position
+ *     points after the flushed buffer which is not necessarily the same
+ *     as after the data you've read.
+ *    - The spout/refill hooks can change not only bptr and bstop, but also
+ *     the location of the buffer; fb-mem.c takes advantage of it.
  */
 
 struct fastbuf {
+  byte is_fastbuf[0];                  /* Dummy field for checking of type casts */
   byte *bptr, *bstop;                  /* Access pointers */
   byte *buffer, *bufend;               /* Start and end of the buffer */
   byte *name;                          /* File name for error messages */
-  uns buflen;                          /* Size of the buffer */
-  sh_off_t pos;                                /* Position of buffer start in the file */
-  sh_off_t fdpos;                      /* Current position in the non-buffered file */
-  int fd;                              /* File descriptor, -1 if not a real file */
-  int is_temp_file;                    /* Is a temporary file, delete on close */
-  void *lldata;                                /* Data private to access functions below */
-  void *llpos;                         /* ... continued ... */
+  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 */
@@ -61,10 +66,18 @@ struct fastbuf {
 
 /* FastIO on standard files */
 
+struct fb_file {
+  struct fastbuf fb;
+  int fd;                              /* File descriptor, -1 if not a real file */
+  int is_temp_file;                    /* 0=normal file, 1=temporary file, delete on close, -1=shared FD */
+};
+#define FB_FILE(f) ((struct fb_file *)(f)->is_fastbuf)
+
 struct fastbuf *bopen(byte *name, uns mode, uns buffer);
 struct fastbuf *bopen_tmp(uns buffer);
 struct fastbuf *bfdopen(int fd, uns buffer);
-void bbcopy(struct fastbuf *f, struct fastbuf *t, uns l);
+struct fastbuf *bfdopen_shared(int fd, uns buffer);
+#define FB_IS_TEMP_FILE(f) FB_FILE(f)->is_temp_file
 
 /* FastIO on in-memory streams */
 
@@ -80,7 +93,7 @@ void bsetpos(struct fastbuf *f, sh_off_t pos);
 
 static inline sh_off_t btell(struct fastbuf *f)
 {
-  return f->pos + (f->bptr - f->buffer);
+  return f->pos + (f->bptr - f->bstop);
 }
 
 int bgetc_slow(struct fastbuf *f);
@@ -272,6 +285,21 @@ bputsn(struct fastbuf *f, byte *b)
   bputc(f, '\n');
 }
 
+void bbcopy_slow(struct fastbuf *f, struct fastbuf *t, uns l);
+static inline void
+bbcopy(struct fastbuf *f, struct fastbuf *t, uns l)
+{
+  if (f->bptr + l <= f->bstop &&
+      t->bptr + l <= t->bufend)
+    {
+      memcpy(t->bptr, f->bptr, l);
+      t->bptr += l;
+      f->bptr += l;
+    }
+  else
+    bbcopy_slow(f, t, l);
+}
+
 /* I/O on addr_int_t */
 
 #ifdef CPU_64BIT_POINTERS
@@ -284,9 +312,34 @@ bputsn(struct fastbuf *f, byte *b)
 
 /* Direct I/O on buffers */
 
-int bdirect_read_prepare(struct fastbuf *f, byte **buf);
-void bdirect_read_commit(struct fastbuf *f, byte *pos);
-int bdirect_write_prepare(struct fastbuf *f, byte **buf);
-void bdirect_write_commit(struct fastbuf *f, byte *pos);
+static inline int
+bdirect_read_prepare(struct fastbuf *f, byte **buf)
+{
+  if (f->bptr == f->bstop && !f->refill(f))
+    return EOF;
+  *buf = f->bptr;
+  return f->bstop - f->bptr;
+}
+
+static inline void
+bdirect_read_commit(struct fastbuf *f, byte *pos)
+{
+  f->bptr = pos;
+}
+
+static inline int
+bdirect_write_prepare(struct fastbuf *f, byte **buf)
+{
+  if (f->bptr == f->bufend)
+    f->spout(f);
+  *buf = f->bptr;
+  return f->bufend - f->bptr;
+}
+
+static inline void
+bdirect_write_commit(struct fastbuf *f, byte *pos)
+{
+  f->bptr = pos;
+}
 
 #endif