fb-file: some comments and automatic tests

diff --git a/lib/Makefile b/lib/Makefile
index 6ef3ef7eb2661ba8b43f9fd012a79232b14b0839..73ec5d3a238bf5272c839b46bcbc699d873f6bca 100644 (file)
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -111,7 +111,7 @@ $(o)/lib/slists.test: $(o)/lib/slists-t
 $(o)/lib/kmp-test.test: $(o)/lib/kmp-test
 $(o)/lib/bbuf.test: $(o)/lib/bbuf-t
 $(o)/lib/getopt.test: $(o)/lib/getopt-t
-$(o)/lib/fastbuf.test: $(o)/lib/fb-grow-t $(o)/lib/fb-pool-t
+$(o)/lib/fastbuf.test: $(o)/lib/fb-file-t $(o)/lib/fb-grow-t $(o)/lib/fb-pool-t
 
 ifdef CONFIG_UCW_THREADS
 TESTS+=$(addprefix $(o)/lib/,asio.test)

diff --git a/lib/fastbuf.t b/lib/fastbuf.t
index 9ac71b58e49bf33d12d58e8bd553a5d33cfaf5de..4771a35e41f79e95879e141f3db607645253cffc 100644 (file)
--- a/lib/fastbuf.t
+++ b/lib/fastbuf.t
@@ -1,5 +1,10 @@
 # Tests for fastbufs
 
+Run:   obj/lib/fb-file-t
+Out:   112
+       <hello><hello><hello><hello><hello><hello><hello><hello><hello><hello><hello><hello><hello><hello><hello><hello>
+       112 116
+
 Run:   obj/lib/fb-grow-t
 Out:   <10><10><0>1234512345<10><9>5<10>
        <10><10><0>1234512345<10><9>5<10>

diff --git a/lib/fb-file.c b/lib/fb-file.c
index 66227ed1b3ef3935ae09c97710b2403b26d66ef7..87791c978a388886f12c3197632e1915fc6be823 100644 (file)
--- a/lib/fb-file.c
+++ b/lib/fb-file.c
@@ -38,24 +38,16 @@ bfd_refill(struct fastbuf *f)
   if (F->wpos <= f->pos)
     {
       sh_off_t diff = f->pos - F->wpos;
-      if (diff > ((sh_off_t)blen << 2)) /* FIXME: Formula for long forward seeks */
+      /* Formula for long forward seeks (prefer lseek()) */
+      if (diff > ((sh_off_t)blen << 2))
         {
 long_seek:
          f->bptr = f->buffer + back;
          f->bstop = f->buffer + blen;
          goto seek;
        }
-      if ((uns)diff < back) /* Reuse part of previous window (also F->wpos == f->pos) */
-        {
-         uns keep = back - (uns)diff;
-         if (keep >= F->wlen)
-           back = diff + (keep = F->wlen);
-         else
-           memmove(f->buffer, f->buffer + F->wlen - keep, keep);
-         read_len -= keep;
-         read_ptr += keep;
-       }
-      else /* Short forward seek */
+      /* Short forward seek (prefer read() to skip data )*/
+      else if ((uns)diff >= back)
         {
          uns skip = diff - back;
          F->wpos += skip;
@@ -73,6 +65,17 @@ long_seek:
              skip -= l;
            }
        }
+      /* Reuse part of the previous window and append new data (also F->wpos == f->pos) */
+      else
+        {
+         uns keep = back - (uns)diff;
+         if (keep >= F->wlen)
+           back = diff + (keep = F->wlen);
+         else
+           memmove(f->buffer, f->buffer + F->wlen - keep, keep);
+         read_len -= keep;
+         read_ptr += keep;
+       }
       f->bptr = f->buffer + back;
       f->bstop = f->buffer + blen;
     }
@@ -80,13 +83,15 @@ long_seek:
   else
     {
       sh_off_t diff = F->wpos - f->pos;
-      if (diff > ((sh_off_t)blen << 1)) /* FIXME: Formula for long backwards seeks */
+      /* Formula for long backwards seeks (keep smaller backbuffer than for shorter seeks ) */
+      if (diff > ((sh_off_t)blen << 1))
         {
          if ((sh_off_t)back > f->pos)
            back = f->pos;
          goto long_seek;
        }
-      if ((uns)diff <= F->wlen) /* Seek into previous window (for example brewind) */
+      /* Seek into previous window (do nothing... for example brewind) */
+      else if ((uns)diff <= F->wlen) 
         {
          f->bstop = f->buffer + F->wlen;
          f->bptr = f->bstop - diff;
@@ -98,7 +103,8 @@ long_seek:
        back = f->pos;
       f->bptr = f->buffer + back;
       read_len = back + diff - F->wlen;
-      if (F->wlen && read_len < blen) /* Reuse part of previous window */
+      /* Reuse part of previous window */
+      if (F->wlen && read_len < blen)
         {
          uns keep = MIN(F->wlen, blen - read_len);
          memmove(f->buffer + read_len, f->buffer, keep);
@@ -107,10 +113,12 @@ long_seek:
       else
        f->bstop = f->buffer + (read_len = blen);
 seek:
+      /* Do lseek() */
       F->wpos = f->pos + (f->buffer - f->bptr);
       if (sh_seek(F->fd, F->wpos, SEEK_SET) < 0)
        die("Error seeking %s: %m", f->name);
     }
+  /* Read (part of) buffer */
   do
     {
       int l = read(F->fd, read_ptr, read_len);
@@ -141,12 +149,14 @@ eof:
 static void
 bfd_spout(struct fastbuf *f)
 {
+  /* Do delayed lseek() if needed */
   if (FB_FILE(f)->wpos != f->pos && sh_seek(FB_FILE(f)->fd, f->pos, SEEK_SET) < 0)
     die("Error seeking %s: %m", f->name);
 
   int l = f->bptr - f->buffer;
   byte *c = f->buffer;
 
+  /* Write the buffer */
   FB_FILE(f)->wpos = (f->pos += l);
   FB_FILE(f)->wlen = 0;
   while (l)
@@ -163,6 +173,7 @@ bfd_spout(struct fastbuf *f)
 static int
 bfd_seek(struct fastbuf *f, sh_off_t pos, int whence)
 {
+  /* Delay the seek for the next refill() or spout() call (if whence != SEEK_END). */
   sh_off_t l;
   switch (whence)
     {
@@ -278,14 +289,17 @@ bfilesync(struct fastbuf *b)
 
 #ifdef TEST
 
-int main(int argc UNUSED, char **argv UNUSED)
+int main(void)
 {
   struct fastbuf *f, *t;
-
-  f = bopen("/etc/profile", O_RDONLY, 16);
+  f = bopen_tmp(16);
   t = bfdopen(1, 13);
-  bbcopy(f, t, 100);
-  printf("%d %d\n", (int)btell(f), (int)btell(t));
+  for (uns i = 0; i < 16; i++)
+    bwrite(f, "<hello>", 7);
+  bprintf(t, "%d\n", (int)btell(f));
+  brewind(f);
+  bbcopy(f, t, ~0U);
+  bprintf(t, "\n%d %d\n", (int)btell(f), (int)btell(t));
   bclose(f);
   bclose(t);
   return 0;