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The symbol table is an ephemeron table

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* libguile/symbols.c: Rework the symbol table to be an ephemeron table
instead of a weak set.  It is no longer resizeable; getting that to work
will involve some GC cooperation.
This commit is contained in:
Andy Wingo 2025-05-14 16:05:29 +02:00
parent dbc384a6ba
commit 4138d3c646
1 changed files with 120 additions and 136 deletions
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256
libguile/symbols.c
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@ -1,4 +1,4 @@
/* Copyright 1995-1998,2000-2001,2003-2004,2006,2009,2011,2013,2015,2018,2022,2023 /* Copyright 1995-1998,2000-2001,2003-2004,2006,2009,2011,2013,2015,2018,2022,2023,2025
Free Software Foundation, Inc. Free Software Foundation, Inc.
This file is part of Guile. This file is part of Guile.
@ -29,6 +29,7 @@
#include "alist.h" #include "alist.h"
#include "boolean.h" #include "boolean.h"
#include "chars.h" #include "chars.h"
#include "ephemerons.h"
#include "eval.h" #include "eval.h"
#include "fluids.h" #include "fluids.h"
#include "gsubr.h" #include "gsubr.h"
@ -46,14 +47,13 @@
#include "threads.h" #include "threads.h"
#include "variable.h" #include "variable.h"
#include "vectors.h" #include "vectors.h"
#include "weak-set.h"
#include "symbols.h" #include "symbols.h"
static SCM symbols; static struct scm_ephemeron_table *symbols;
#ifdef GUILE_DEBUG #ifdef GUILE_DEBUG
SCM_DEFINE (scm_sys_symbols, "%symbols", 0, 0, 0, SCM_DEFINE (scm_sys_symbols, "%symbols", 0, 0, 0,
@ -61,7 +61,7 @@ SCM_DEFINE (scm_sys_symbols, "%symbols", 0, 0, 0,
"Return the system symbol obarray.") "Return the system symbol obarray.")
#define FUNC_NAME s_scm_sys_symbols #define FUNC_NAME s_scm_sys_symbols
{ {
return symbols; return scm_from_ephemeron_table (symbols);
} }
#undef FUNC_NAME #undef FUNC_NAME
#endif #endif
@ -77,187 +77,171 @@ scm_i_hash_symbol (SCM obj, unsigned long n, void *closure)
return scm_i_symbol_hash (obj) % n; return scm_i_symbol_hash (obj) % n;
} }
struct string_lookup_data
{
SCM string;
unsigned long string_hash;
};
static int static int
string_lookup_predicate_fn (SCM sym, void *closure) symbol_equals_string (SCM sym, SCM str, size_t len, unsigned long hash)
{ {
struct string_lookup_data *data = closure; if (scm_i_symbol_hash (sym) != hash)
return 0;
if (scm_i_symbol_hash (sym) == data->string_hash if (scm_i_symbol_length (sym) != len)
&& scm_i_symbol_length (sym) == scm_i_string_length (data->string))
{
size_t n = scm_i_symbol_length (sym);
while (n--)
if (scm_i_symbol_ref (sym, n) != scm_i_string_ref (data->string, n))
return 0;
return 1;
}
else
return 0; return 0;
}
static SCM
lookup_interned_symbol (SCM name, unsigned long raw_hash)
{
struct string_lookup_data data;
data.string = name;
data.string_hash = raw_hash;
return scm_c_weak_set_lookup (symbols, raw_hash, for (size_t i = 0; i < len; i++)
string_lookup_predicate_fn, if (scm_i_symbol_ref (sym, i) != scm_i_string_ref (str, i))
&data, SCM_BOOL_F); return 0;
}
struct latin1_lookup_data return 1;
{ }
const char *str;
size_t len;
unsigned long string_hash;
};
static int static int
latin1_lookup_predicate_fn (SCM sym, void *closure) symbol_equals_latin1_string (SCM sym, const char *str, size_t len,
unsigned long hash)
{ {
struct latin1_lookup_data *data = closure; if (scm_i_symbol_hash (sym) != hash)
return 0;
return scm_i_symbol_hash (sym) == data->string_hash if (scm_i_symbol_length (sym) != len)
&& scm_i_is_narrow_symbol (sym) return 0;
&& scm_i_symbol_length (sym) == data->len if (!scm_i_is_narrow_symbol (sym))
&& strncmp (scm_i_symbol_chars (sym), data->str, data->len) == 0; return 0;
return strncmp (scm_i_symbol_chars (sym), str, len) == 0;
} }
static SCM static SCM
lookup_interned_latin1_symbol (const char *str, size_t len, lookup_interned_latin1_symbol (const char *str, size_t len,
unsigned long raw_hash) unsigned long raw_hash)
{ {
struct latin1_lookup_data data; size_t bucket = raw_hash % scm_c_ephemeron_table_length (symbols);
for (struct gc_ephemeron *e = scm_c_ephemeron_table_ref (symbols, bucket);
data.str = str; e;
data.len = len; e = scm_c_ephemeron_next (e))
data.string_hash = raw_hash; {
SCM sym = scm_c_ephemeron_key (e);
return scm_c_weak_set_lookup (symbols, raw_hash, if (scm_is_true (sym)
latin1_lookup_predicate_fn, && symbol_equals_latin1_string (sym, str, len, raw_hash))
&data, SCM_BOOL_F); return sym;
}
return SCM_BOOL_F;
} }
struct utf8_lookup_data
{
const char *str;
size_t len;
unsigned long string_hash;
};
static int static int
utf8_string_equals_wide_string (const uint8_t *narrow, size_t nlen, utf8_string_equals_narrow_string (const uint8_t *utf8, size_t ulen,
const scm_t_wchar *wide, size_t wlen) const char *narrow)
{ {
size_t byte_idx = 0, char_idx = 0; /* Precondition: utf8,ulen is valid UTF-8. */
size_t byte_idx = 0;
while (byte_idx < nlen && char_idx < wlen) while (byte_idx < ulen)
{ {
ucs4_t c; ucs4_t c = -1;
int nbytes; byte_idx += u8_mbtoucr (&c, utf8 + byte_idx, ulen - byte_idx);
if (c != *narrow)
nbytes = u8_mbtoucr (&c, narrow + byte_idx, nlen - byte_idx);
if (nbytes == 0)
break;
else if (nbytes < 0)
/* Bad UTF-8. */
return 0; return 0;
else if (c != wide[char_idx]) narrow++;
return 0;
byte_idx += nbytes;
char_idx++;
} }
return byte_idx == nlen && char_idx == wlen; return 1;
} }
static int static int
utf8_lookup_predicate_fn (SCM sym, void *closure) utf8_string_equals_wide_string (const uint8_t *utf8, size_t ulen,
const scm_t_wchar *wide)
{ {
struct utf8_lookup_data *data = closure; /* Precondition: utf8,ulen is valid UTF-8. */
size_t byte_idx = 0;
while (byte_idx < ulen)
{
ucs4_t c = -1;
byte_idx += u8_mbtoucr (&c, utf8 + byte_idx, ulen - byte_idx);
if (c != *wide)
return 0;
wide++;
}
if (scm_i_symbol_hash (sym) != data->string_hash) return 1;
}
static int
symbol_equals_utf8_string (SCM sym, const uint8_t *str, size_t len,
unsigned long hash, int codepoint_count)
{
if (scm_i_symbol_hash (sym) != hash)
return 0;
if (scm_i_symbol_length (sym) != codepoint_count)
return 0; return 0;
if (scm_i_is_narrow_symbol (sym)) if (scm_i_is_narrow_symbol (sym))
return (scm_i_symbol_length (sym) == data->len return utf8_string_equals_narrow_string (str, len,
&& strncmp (scm_i_symbol_chars (sym), data->str, data->len) == 0); scm_i_symbol_chars (sym));
else else
return utf8_string_equals_wide_string ((const uint8_t *) data->str, return utf8_string_equals_wide_string (str, len,
data->len, scm_i_symbol_wide_chars (sym));
scm_i_symbol_wide_chars (sym),
scm_i_symbol_length (sym));
} }
static SCM static SCM
lookup_interned_utf8_symbol (const char *str, size_t len, lookup_interned_utf8_symbol (const uint8_t *str, size_t len,
unsigned long raw_hash) unsigned long raw_hash)
{ {
struct utf8_lookup_data data; int codepoint_count = u8_mbsnlen (str, len);
if (codepoint_count == -1)
/* Bad UTF-8. */
return SCM_BOOL_F;
data.str = str; if (codepoint_count == len)
data.len = len; return lookup_interned_latin1_symbol ((const char *) str, len, raw_hash);
data.string_hash = raw_hash;
return scm_c_weak_set_lookup (symbols, raw_hash,
utf8_lookup_predicate_fn,
&data, SCM_BOOL_F);
}
static int size_t bucket = raw_hash % scm_c_ephemeron_table_length (symbols);
symbol_lookup_predicate_fn (SCM sym, void *closure) for (struct gc_ephemeron *e = scm_c_ephemeron_table_ref (symbols, bucket);
{ e;
SCM other = SCM_PACK_POINTER (closure); e = scm_c_ephemeron_next (e))
if (scm_i_symbol_hash (sym) == scm_i_symbol_hash (other)
&& scm_i_symbol_length (sym) == scm_i_symbol_length (other))
{ {
if (scm_i_is_narrow_symbol (sym)) SCM sym = scm_c_ephemeron_key (e);
return scm_i_is_narrow_symbol (other) if (scm_is_true (sym)
&& (strncmp (scm_i_symbol_chars (sym), && symbol_equals_utf8_string (sym, str, len, raw_hash,
scm_i_symbol_chars (other), codepoint_count))
scm_i_symbol_length (other)) == 0); return sym;
else
return scm_is_true
(scm_string_equal_p (scm_symbol_to_string (sym),
scm_symbol_to_string (other)));
} }
return 0; return SCM_BOOL_F;
} }
static SCM static SCM
scm_i_str2symbol (SCM str) scm_i_str2symbol (SCM str)
{ {
SCM symbol;
unsigned long raw_hash = scm_i_string_hash (str); unsigned long raw_hash = scm_i_string_hash (str);
size_t bucket = raw_hash % scm_c_ephemeron_table_length (symbols);
size_t len = scm_i_string_length (str);
symbol = lookup_interned_symbol (str, raw_hash); struct gc_ephemeron *chain = scm_c_ephemeron_table_ref (symbols, bucket);
if (scm_is_true (symbol)) /* First see if a symbol with this name is already interned. */
return symbol; for (struct gc_ephemeron *e = chain; e; e = scm_c_ephemeron_next (e))
else
{ {
/* The symbol was not found, create it. */ SCM sym = scm_c_ephemeron_key (e);
symbol = scm_i_make_symbol (str, 0, raw_hash); if (scm_is_true (sym) && symbol_equals_string (sym, str, len, raw_hash))
return sym;
/* Might return a different symbol, if another one was interned at }
the same time. */
return scm_c_weak_set_add_x (symbols, raw_hash, /* The symbol was not found, create it. */
symbol_lookup_predicate_fn, SCM sym = scm_i_make_symbol (str, 0, raw_hash);
SCM_UNPACK_POINTER (symbol), symbol); struct gc_ephemeron *link = scm_c_make_ephemeron (sym, SCM_BOOL_T);
while (1)
{
struct gc_ephemeron *prev =
scm_c_ephemeron_table_try_push_x (symbols, bucket, link, chain);
if (prev == chain)
return sym;
/* Lost a race, someone else added a symbol in this bucket. Check
the chain and try again. */
chain = prev;
for (struct gc_ephemeron *e = chain; e; e = scm_c_ephemeron_next (e))
{
SCM sym = scm_c_ephemeron_key (e);
if (scm_is_true (sym)
&& symbol_equals_string (sym, str, len, raw_hash))
return sym;
}
} }
} }
static SCM static SCM
scm_i_str2uninterned_symbol (SCM str) scm_i_str2uninterned_symbol (SCM str)
{ {
@ -449,7 +433,7 @@ scm_from_utf8_symboln (const char *sym, size_t len)
len = strlen (sym); len = strlen (sym);
hash = scm_i_utf8_string_hash (sym, len); hash = scm_i_utf8_string_hash (sym, len);
ret = lookup_interned_utf8_symbol (sym, len, hash); ret = lookup_interned_utf8_symbol ((const uint8_t *)sym, len, hash);
if (scm_is_false (ret)) if (scm_is_false (ret))
{ {
SCM str = scm_from_utf8_stringn (sym, len); SCM str = scm_from_utf8_stringn (sym, len);
@ -462,7 +446,7 @@ scm_from_utf8_symboln (const char *sym, size_t len)
void void
scm_symbols_prehistory () scm_symbols_prehistory ()
{ {
symbols = scm_c_make_weak_set (5000); symbols = scm_c_make_ephemeron_table (5000);
} }