Always define the memory allocation primitives with the `sh_' prefix,

[libucw.git] / lib / fastbuf.h

diff --git a/lib/fastbuf.h b/lib/fastbuf.h
index 9e974cf54ea4539b7c6d9f29d19b970f42c17246..777630c8b92d146c265cb4455d50a0bbe77fc312 100644 (file)
--- a/lib/fastbuf.h
+++ b/lib/fastbuf.h
@@ -51,6 +51,17 @@
  *     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.
+ *    - In some cases, the user of the bdirect interface can be allowed to modify
+ *     the data in the buffer to avoid unnecessary copying. If the back-end
+ *     allows such modifications, it can set can_overwrite_buffer accordingly:
+ *             *  0 if no modification is allowed,
+ *             *  1 if the user can modify the buffer on the condition that
+ *                  the modifications will be undone before calling the next
+ *                  fastbuf operation
+ *             *  2 if the user is allowed to overwrite the data in the buffer
+ *                  if bdirect_read_commit_modified() is called afterwards.
+ *                  In this case, the back-end must be prepared for trimming
+ *                  of the buffer which is done by the commit function.
  */
 
 struct fastbuf {
@@ -64,14 +75,16 @@ struct fastbuf {
   void (*seek)(struct fastbuf *, sh_off_t, int);  /* Slow path for bseek(), buffer already flushed */
   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 */
 };
 
 /* FastIO on standard files (specify buffer size 0 to enable mmaping) */
 
-struct fastbuf *bopen(byte *name, uns mode, uns buffer);
-struct fastbuf *bopen_tmp(uns buffer);
-struct fastbuf *bfdopen(int fd, uns buffer);
-struct fastbuf *bfdopen_shared(int fd, uns buffer);
+struct fastbuf *bopen(byte *name, uns mode, uns buflen);
+struct fastbuf *bopen_tmp(uns buflen);
+struct fastbuf *bfdopen(int fd, uns buflen);
+struct fastbuf *bfdopen_shared(int fd, uns buflen);
+void bfilesync(struct fastbuf *b);
 
 /* FastIO on in-memory streams */
 
@@ -88,7 +101,7 @@ struct fastbuf *bopen_limited_fd(int fd, uns bufsize, uns limit);
 
 /* FastIO on static buffers */
 
-void fbbuf_init_read(struct fastbuf *f, byte *buffer, uns size);
+void fbbuf_init_read(struct fastbuf *f, byte *buffer, uns size, uns can_overwrite);
 void fbbuf_init_write(struct fastbuf *f, byte *buffer, uns size);
 static inline uns
 fbbuf_count_written(struct fastbuf *f)
@@ -101,16 +114,6 @@ fbbuf_count_written(struct fastbuf *f)
 int bconfig(struct fastbuf *f, uns type, int data);
 
 #define BCONFIG_IS_TEMP_FILE 0
-#define BCONFIG_CAN_OVERWRITE 1
-  /* Specifies whether the caller is allowed to perform the following optimized
-   * 0-copy write operation:
-   *   - get the buffer by bdirect_read_prepare()
-   *   - modify the buffer, e.g. by putting \0's inside
-   *   - call bflush() to let the fastbuf know
-   * Values:
-   * 0: read-only memory
-   * 1: you can write into read-write memory, if you restore the original value
-   * 2: you can rewrite the original content */
 
 /* Universal functions working on all fastbuf's */
 
@@ -119,7 +122,8 @@ 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);
-void bskip(struct fastbuf *f, uns len);
+int bskip(struct fastbuf *f, uns len);
+sh_off_t bfilesize(struct fastbuf *f);
 
 static inline sh_off_t btell(struct fastbuf *f)
 {
@@ -152,11 +156,23 @@ static inline void bputc(struct fastbuf *f, uns c)
     bputc_slow(f, c);
 }
 
+static inline uns
+bavailr(struct fastbuf *f)
+{
+  return f->bstop - f->bptr;
+}
+
+static inline uns
+bavailw(struct fastbuf *f)
+{
+  return f->bufend - f->bptr;
+}
+
 int bgetw_slow(struct fastbuf *f);
 static inline int bgetw(struct fastbuf *f)
 {
   int w;
-  if (f->bptr + 2 <= f->bstop)
+  if (bavailr(f) >= 2)
     {
       w = GET_U16(f->bptr);
       f->bptr += 2;
@@ -170,7 +186,7 @@ u32 bgetl_slow(struct fastbuf *f);
 static inline u32 bgetl(struct fastbuf *f)
 {
   u32 l;
-  if (f->bptr + 4 <= f->bstop)
+  if (bavailr(f) >= 4)
     {
       l = GET_U32(f->bptr);
       f->bptr += 4;
@@ -184,7 +200,7 @@ u64 bgetq_slow(struct fastbuf *f);
 static inline u64 bgetq(struct fastbuf *f)
 {
   u64 l;
-  if (f->bptr + 8 <= f->bstop)
+  if (bavailr(f) >= 8)
     {
       l = GET_U64(f->bptr);
       f->bptr += 8;
@@ -198,7 +214,7 @@ u64 bget5_slow(struct fastbuf *f);
 static inline u64 bget5(struct fastbuf *f)
 {
   u64 l;
-  if (f->bptr + 5 <= f->bstop)
+  if (bavailr(f) >= 5)
     {
       l = GET_U40(f->bptr);
       f->bptr += 5;
@@ -211,7 +227,7 @@ static inline u64 bget5(struct fastbuf *f)
 void bputw_slow(struct fastbuf *f, uns w);
 static inline void bputw(struct fastbuf *f, uns w)
 {
-  if (f->bptr + 2 <= f->bufend)
+  if (bavailw(f) >= 2)
     {
       PUT_U16(f->bptr, w);
       f->bptr += 2;
@@ -223,7 +239,7 @@ static inline void bputw(struct fastbuf *f, uns w)
 void bputl_slow(struct fastbuf *f, u32 l);
 static inline void bputl(struct fastbuf *f, u32 l)
 {
-  if (f->bptr + 4 <= f->bufend)
+  if (bavailw(f) >= 4)
     {
       PUT_U32(f->bptr, l);
       f->bptr += 4;
@@ -235,7 +251,7 @@ static inline void bputl(struct fastbuf *f, u32 l)
 void bputq_slow(struct fastbuf *f, u64 l);
 static inline void bputq(struct fastbuf *f, u64 l)
 {
-  if (f->bptr + 8 <= f->bufend)
+  if (bavailw(f) >= 8)
     {
       PUT_U64(f->bptr, l);
       f->bptr += 8;
@@ -247,7 +263,7 @@ static inline void bputq(struct fastbuf *f, u64 l)
 void bput5_slow(struct fastbuf *f, u64 l);
 static inline void bput5(struct fastbuf *f, u64 l)
 {
-  if (f->bptr + 5 <= f->bufend)
+  if (bavailw(f) >= 5)
     {
       PUT_U40(f->bptr, l);
       f->bptr += 5;
@@ -259,7 +275,7 @@ static inline void bput5(struct fastbuf *f, u64 l)
 uns bread_slow(struct fastbuf *f, void *b, uns l, uns check);
 static inline uns bread(struct fastbuf *f, void *b, uns l)
 {
-  if (f->bptr + l <= f->bstop)
+  if (bavailr(f) >= l)
     {
       memcpy(b, f->bptr, l);
       f->bptr += l;
@@ -271,7 +287,7 @@ static inline uns bread(struct fastbuf *f, void *b, uns l)
 
 static inline uns breadb(struct fastbuf *f, void *b, uns l)
 {
-  if (f->bptr + l <= f->bstop)
+  if (bavailr(f) >= l)
     {
       memcpy(b, f->bptr, l);
       f->bptr += l;
@@ -284,7 +300,7 @@ static inline uns breadb(struct fastbuf *f, void *b, uns l)
 void bwrite_slow(struct fastbuf *f, void *b, uns l);
 static inline void bwrite(struct fastbuf *f, void *b, uns l)
 {
-  if (f->bptr + l <= f->bufend)
+  if (bavailw(f) >= l)
     {
       memcpy(f->bptr, b, l);
       f->bptr += l;
@@ -320,8 +336,7 @@ 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)
+  if (bavailr(f) >= l && bavailw(t) >= l)
     {
       memcpy(t->bptr, f->bptr, l);
       t->bptr += l;
@@ -349,7 +364,7 @@ bdirect_read_prepare(struct fastbuf *f, byte **buf)
   if (f->bptr == f->bstop && !f->refill(f))
     return 0;
   *buf = f->bptr;
-  return f->bstop - f->bptr;
+  return bavailr(f);
 }
 
 static inline void
@@ -358,13 +373,20 @@ bdirect_read_commit(struct fastbuf *f, byte *pos)
   f->bptr = pos;
 }
 
+static inline void
+bdirect_read_commit_modified(struct fastbuf *f, byte *pos)
+{
+  f->bptr = pos;
+  f->buffer = pos;     /* Avoid seeking backwards in the buffer */
+}
+
 static inline uns
 bdirect_write_prepare(struct fastbuf *f, byte **buf)
 {
   if (f->bptr == f->bufend)
     f->spout(f);
   *buf = f->bptr;
-  return f->bufend - f->bptr;
+  return bavailw(f);
 }
 
 static inline void