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Revert "Universally-unique gensyms"

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This reverts commit ad432bc831.

Not all gensyms need to be universally-unique: most of them just need to
be unique within some portion of a Guile session.  We'll take a
different tack on this problem in the next commit.
This commit is contained in:
Andy Wingo 2012-01-26 11:00:55 +01:00
parent d062a8c1ee
commit 4496c9c1e8
3 changed files with 11 additions and 44 deletions
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50
libguile/symbols.c
View file

@ -31,7 +31,6 @@
#include "libguile/variable.h"
#include "libguile/alist.h"
#include "libguile/fluids.h"
#include "libguile/threads.h"
#include "libguile/strings.h"
#include "libguile/vectors.h"
#include "libguile/hashtab.h"
@ -341,9 +340,7 @@ SCM_DEFINE (scm_string_ci_to_symbol, "string-ci->symbol", 1, 0, 0,
/* The default prefix for `gensym'd symbols. */
static SCM default_gensym_prefix;
#define GENSYM_LENGTH 22 /* bytes */
#define GENSYM_RADIX_BITS 6
#define GENSYM_RADIX (1 << (GENSYM_RADIX_BITS))
#define MAX_PREFIX_LENGTH 30
SCM_DEFINE (scm_gensym, "gensym", 0, 1, 0,
(SCM prefix),
@ -354,47 +351,22 @@ SCM_DEFINE (scm_gensym, "gensym", 0, 1, 0,
"resetting the counter.")
#define FUNC_NAME s_scm_gensym
{
static const char base64[GENSYM_RADIX] =
"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789$@";
static const char base4[4] = "_.-~";
unsigned char *digit_buf = SCM_I_CURRENT_THREAD->gensym_counter;
char char_buf[GENSYM_LENGTH];
static int gensym_counter = 0;
SCM suffix, name;
int i;
int n, n_digits;
char buf[SCM_INTBUFLEN];
if (SCM_UNBNDP (prefix))
prefix = default_gensym_prefix;
if (SCM_UNLIKELY (digit_buf == NULL))
{
/* This is the first time gensym has been called in this thread.
Allocate and randomize our new thread-local gensym counter */
digit_buf = (unsigned char *)
scm_gc_malloc_pointerless (GENSYM_LENGTH, "gensym-counter");
scm_i_random_bytes_from_platform (digit_buf, GENSYM_LENGTH);
for (i = (GENSYM_LENGTH - 1); i >= 0; --i)
digit_buf[i] &= (GENSYM_RADIX - 1);
SCM_I_CURRENT_THREAD->gensym_counter = digit_buf;
}
/* mutex in case another thread looks and incs at the exact same moment */
scm_i_scm_pthread_mutex_lock (&scm_i_misc_mutex);
n = gensym_counter++;
scm_i_pthread_mutex_unlock (&scm_i_misc_mutex);
/* Increment our thread-local gensym_counter. */
for (i = (GENSYM_LENGTH - 1); i >= 0; --i)
{
if (SCM_LIKELY (++(digit_buf[i]) < GENSYM_RADIX))
break;
else
digit_buf[i] = 0;
}
/* Encode digit_buf as base64, except for the first character where we
use the sparse glyphs "_.-~" (base 4) to provide some visual
separation between the prefix and the dense base64 block. */
for (i = (GENSYM_LENGTH - 1); i > 0; --i)
char_buf[i] = base64[digit_buf[i]];
char_buf[0] = base4[digit_buf[0] & 3];
suffix = scm_from_latin1_stringn (char_buf, GENSYM_LENGTH);
n_digits = scm_iint2str (n, 10, buf);
suffix = scm_from_latin1_stringn (buf, n_digits);
name = scm_string_append (scm_list_2 (prefix, suffix));
return scm_string_to_symbol (name);
}

1
libguile/threads.c
View file

@ -545,7 +545,6 @@ guilify_self_1 (struct GC_stack_base *base)
t.join_queue = SCM_EOL;
t.dynamic_state = SCM_BOOL_F;
t.dynwinds = SCM_EOL;
t.gensym_counter = NULL;
t.active_asyncs = SCM_EOL;
t.block_asyncs = 1;
t.pending_asyncs = 1;

4
libguile/threads.h
View file

@ -81,10 +81,6 @@ typedef struct scm_i_thread {
SCM dynamic_state;
SCM dynwinds;
/* Thread-local gensym counter.
*/
unsigned char *gensym_counter;
/* For system asyncs.
*/
SCM active_asyncs; /* The thunks to be run at the next