From 49edfa12025a3552d1cfcd2a936201c1da95148a Mon Sep 17 00:00:00 2001 From: Martin Mares Date: Mon, 28 Jun 2004 15:06:40 +0000 Subject: [PATCH] A better implementation of overwritable buffers. --- lib/bucket.c | 21 +++------------------ lib/fastbuf.h | 37 +++++++++++++++++++++++-------------- lib/fb-buffer.c | 19 ++++--------------- lib/fb-file.c | 33 ++++++++++++++------------------- lib/fb-limfd.c | 19 +------------------ lib/fb-mem.c | 20 +------------------- lib/fb-mmap.c | 2 -- lib/fb-temp.c | 4 ++-- 8 files changed, 48 insertions(+), 107 deletions(-) diff --git a/lib/bucket.c b/lib/bucket.c index 4a5533cf..fa4f5ded 100644 --- a/lib/bucket.c +++ b/lib/bucket.c @@ -131,7 +131,6 @@ obuck_unlock(void) struct fb_bucket { struct fastbuf fb; - int can_overwrite; sh_off_t start_pos; uns bucket_size; byte buffer[0]; @@ -302,21 +301,6 @@ obuck_find_next(struct obuck_header *hdrp, int full) } } -static int -obuck_bconfig(struct fastbuf *f, uns item, int value) -{ - switch (item) - { - case BCONFIG_CAN_OVERWRITE: ; - int old_value = FB_BUCKET(f)->can_overwrite; - if (value >= 0 && value <= 2) - FB_BUCKET(f)->can_overwrite = value; - return old_value; - default: - return -1; - } -} - struct fastbuf * obuck_fetch(void) { @@ -333,7 +317,8 @@ obuck_fetch(void) b->spout = NULL; b->seek = NULL; b->close = obuck_fb_close; - b->config = obuck_bconfig; + b->config = NULL; + b->can_overwrite_buffer = 2; FB_BUCKET(b)->start_pos = bucket_find_pos; FB_BUCKET(b)->bucket_size = obuck_hdr.length; obuck_fb_count++; @@ -373,9 +358,9 @@ obuck_create(u32 type) b->seek = NULL; b->close = NULL; b->config = NULL; + b->can_overwrite_buffer = 0; FB_BUCKET(b)->start_pos = start; FB_BUCKET(b)->bucket_size = 0; - FB_BUCKET(b)->can_overwrite = 2; bwrite(b, &obuck_create_hdr, sizeof(obuck_create_hdr)); return b; diff --git a/lib/fastbuf.h b/lib/fastbuf.h index 9e974cf5..45ce0691 100644 --- 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 +75,15 @@ 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); /* FastIO on in-memory streams */ @@ -101,16 +113,6 @@ 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 */ @@ -358,6 +360,13 @@ 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) { diff --git a/lib/fb-buffer.c b/lib/fb-buffer.c index 2f52665f..5a248efd 100644 --- a/lib/fb-buffer.c +++ b/lib/fb-buffer.c @@ -11,19 +11,6 @@ #include "lib/lib.h" #include "lib/fastbuf.h" -static int -fbbuf_config(struct fastbuf *f UNUSED, uns item, int value UNUSED) -{ - switch (item) - { - case BCONFIG_CAN_OVERWRITE: - // XXX: should we enable changing the value? - return 1; - default: - return -1; - } -} - static int fbbuf_refill(struct fastbuf *f UNUSED) { @@ -41,7 +28,8 @@ fbbuf_init_read(struct fastbuf *f, byte *buf, uns size) f->spout = NULL; f->seek = NULL; f->close = NULL; - f->config = fbbuf_config; + f->config = NULL; + f->can_overwrite_buffer = 1; } static void @@ -61,5 +49,6 @@ fbbuf_init_write(struct fastbuf *f, byte *buf, uns size) f->spout = fbbuf_spout; f->seek = NULL; f->close = NULL; - f->config = fbbuf_config; + f->config = NULL; + f->can_overwrite_buffer = 0; } diff --git a/lib/fb-file.c b/lib/fb-file.c index c33698e9..169f25e1 100644 --- a/lib/fb-file.c +++ b/lib/fb-file.c @@ -1,7 +1,7 @@ /* * Sherlock Library -- Fast Buffered I/O on Files * - * (c) 1997--2002 Martin Mares + * (c) 1997--2004 Martin Mares * (c) 2004 Robert Spalek * * This software may be freely distributed and used according to the terms @@ -21,17 +21,17 @@ 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 */ - int can_overwrite; }; #define FB_FILE(f) ((struct fb_file *)(f)->is_fastbuf) +#define FB_BUFFER(f) (byte *)(FB_FILE(f) + 1) static int bfd_refill(struct fastbuf *f) { + f->bptr = f->buffer = FB_BUFFER(f); int l = read(FB_FILE(f)->fd, f->buffer, f->bufend-f->buffer); if (l < 0) die("Error reading %s: %m", f->name); - f->bptr = f->buffer; f->bstop = f->buffer + l; f->pos += l; return l; @@ -41,7 +41,7 @@ static void bfd_spout(struct fastbuf *f) { int l = f->bptr - f->buffer; - char *c = f->buffer; + byte *c = f->buffer; f->pos += l; while (l) @@ -52,7 +52,7 @@ bfd_spout(struct fastbuf *f) l -= z; c += z; } - f->bptr = f->buffer; + f->bptr = f->buffer = FB_BUFFER(f); } static void @@ -91,11 +91,6 @@ bfd_config(struct fastbuf *f, uns item, int value) case BCONFIG_IS_TEMP_FILE: FB_FILE(f)->is_temp_file = value; return 0; - case BCONFIG_CAN_OVERWRITE: ; - int old_value = FB_FILE(f)->can_overwrite; - if (value >= 0 && value <= 2) - FB_FILE(f)->can_overwrite = value; - return old_value; default: return -1; } @@ -109,7 +104,7 @@ bfdopen_internal(int fd, uns buflen, byte *name) struct fastbuf *f = &F->fb; bzero(F, sizeof(*F)); - f->buffer = (char *)(F+1); + f->buffer = (byte *)(F+1); f->bptr = f->bstop = f->buffer; f->bufend = f->buffer + buflen; f->name = f->bufend; @@ -120,41 +115,41 @@ bfdopen_internal(int fd, uns buflen, byte *name) f->seek = bfd_seek; f->close = bfd_close; f->config = bfd_config; - F->can_overwrite = 2; + f->can_overwrite_buffer = 2; return f; } struct fastbuf * -bopen(byte *name, uns mode, uns buffer) +bopen(byte *name, uns mode, uns buflen) { struct fastbuf *b; int fd; - if (!buffer) + if (!buflen) return bopen_mm(name, mode); fd = sh_open(name, mode, 0666); if (fd < 0) die("Unable to %s file %s: %m", (mode & O_CREAT) ? "create" : "open", name); - b = bfdopen_internal(fd, buffer, name); + b = bfdopen_internal(fd, buflen, name); if (mode & O_APPEND) bfd_seek(b, 0, SEEK_END); return b; } struct fastbuf * -bfdopen(int fd, uns buffer) +bfdopen(int fd, uns buflen) { byte x[32]; sprintf(x, "fd%d", fd); - return bfdopen_internal(fd, buffer, x); + return bfdopen_internal(fd, buflen, x); } struct fastbuf * -bfdopen_shared(int fd, uns buffer) +bfdopen_shared(int fd, uns buflen) { - struct fastbuf *f = bfdopen(fd, buffer); + struct fastbuf *f = bfdopen(fd, buflen); FB_FILE(f)->is_temp_file = -1; return f; } diff --git a/lib/fb-limfd.c b/lib/fb-limfd.c index 7e07e328..745445a2 100644 --- a/lib/fb-limfd.c +++ b/lib/fb-limfd.c @@ -18,7 +18,6 @@ struct fb_limfd { struct fastbuf fb; int fd; /* File descriptor */ int limit; - int can_overwrite; }; #define FB_LIMFD(f) ((struct fb_limfd *)(f)->is_fastbuf) @@ -41,21 +40,6 @@ bfl_close(struct fastbuf *f) xfree(f); } -static int -bfl_config(struct fastbuf *f, uns item, int value) -{ - switch (item) - { - case BCONFIG_CAN_OVERWRITE: ; - int old_value = FB_LIMFD(f)->can_overwrite; - if (value >= 0 && value <= 2) - FB_LIMFD(f)->can_overwrite = value; - return old_value; - default: - return -1; - } -} - struct fastbuf * bopen_limited_fd(int fd, uns buflen, uns limit) { @@ -71,8 +55,7 @@ bopen_limited_fd(int fd, uns buflen, uns limit) F->limit = limit; f->refill = bfl_refill; f->close = bfl_close; - f->config = bfl_config; - F->can_overwrite = 2; + f->can_overwrite_buffer = 2; return f; } diff --git a/lib/fb-mem.c b/lib/fb-mem.c index 82fe251e..89390f1b 100644 --- a/lib/fb-mem.c +++ b/lib/fb-mem.c @@ -30,7 +30,6 @@ struct fb_mem { struct fastbuf fb; struct memstream *stream; struct msblock *block; - int can_overwrite; }; #define FB_MEM(f) ((struct fb_mem *)(f)->is_fastbuf) @@ -151,21 +150,6 @@ fbmem_close(struct fastbuf *f) xfree(f); } -static int -fbmem_config(struct fastbuf *f, uns item, int value) -{ - switch (item) - { - case BCONFIG_CAN_OVERWRITE: ; - int old_value = FB_MEM(f)->can_overwrite; - if (value >= 0 && value <= 1) - FB_MEM(f)->can_overwrite = value; - return old_value; - default: - return -1; - } -} - struct fastbuf * fbmem_create(unsigned blocksize) { @@ -179,7 +163,6 @@ fbmem_create(unsigned blocksize) f->name = ""; f->spout = fbmem_spout; f->close = fbmem_close; - f->config = fbmem_config; return f; } @@ -197,8 +180,7 @@ fbmem_clone_read(struct fastbuf *b) f->refill = fbmem_refill; f->seek = fbmem_seek; f->close = fbmem_close; - f->config = fbmem_config; - FB_MEM(f)->can_overwrite = 1; + f->can_overwrite_buffer = 1; return f; } diff --git a/lib/fb-mmap.c b/lib/fb-mmap.c index bbd3a11e..b6f82775 100644 --- a/lib/fb-mmap.c +++ b/lib/fb-mmap.c @@ -160,8 +160,6 @@ bfmm_config(struct fastbuf *f, uns item, int value) case BCONFIG_IS_TEMP_FILE: FB_MMAP(f)->is_temp_file = value; return 0; - case BCONFIG_CAN_OVERWRITE: - return 0; /* cannot use 1, because the pages would become dirty */ default: return -1; } diff --git a/lib/fb-temp.c b/lib/fb-temp.c index a537dd93..f7b14483 100644 --- a/lib/fb-temp.c +++ b/lib/fb-temp.c @@ -28,14 +28,14 @@ static void CONSTRUCTOR temp_init_config(void) } struct fastbuf * -bopen_tmp(uns bufsize) +bopen_tmp(uns buflen) { byte buf[256]; struct fastbuf *f; static uns temp_counter; sprintf(buf, temp_template, (int) getpid(), temp_counter++); - f = bopen(buf, O_RDWR | O_CREAT | O_TRUNC, bufsize); + f = bopen(buf, O_RDWR | O_CREAT | O_TRUNC, buflen); bconfig(f, BCONFIG_IS_TEMP_FILE, 1); return f; } -- 2.39.2