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/cmake-build-debug | ||
/cmake-build-release |
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cmake_minimum_required(VERSION 3.20) | ||
project(cii C) | ||
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set(CMAKE_C_STANDARD 11) | ||
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set(SOURCE_FILES | ||
src/atom.c | ||
) | ||
set(HEADER_FILES | ||
include/cii/atom.h | ||
) | ||
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add_library(cii STATIC | ||
${SOURCE_FILES} | ||
${HEADER_FILES} | ||
) | ||
target_include_directories(cii | ||
PUBLIC include | ||
) |
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// Copyright (c) 2023 Xu Shaohua <[email protected]>. All rights reserved. | ||
// Use of this source is governed by GNU General Public License | ||
// that can be found in the LICENSE file. | ||
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#ifndef CII_ATOM_H_ | ||
#define CII_ATOM_H_ | ||
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/** | ||
* An atom is a pointer to a unique, immutable sequence of zero or more | ||
* arbitrary bytes. Most atoms are null-terminated strings, but a pointer to | ||
* any sequence of bytes can be an atom. | ||
* | ||
* There is only a single occurrence(instance) of any atom, which is why it's | ||
* called an atom. | ||
* | ||
* Two atoms are identical if they point to the same location. Comparing two byte | ||
* sequences for equality by simply comparing pointers is one of the advantages | ||
* of atoms. Another advantage is that using atoms saves space because there's | ||
* only one occurrence of each sequence. | ||
* | ||
* Once an atom is created, it exists for the duration of the client's execution. | ||
* An atom is always terminated with a null character. | ||
*/ | ||
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#include <stdint.h> | ||
#include <stddef.h> | ||
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/** | ||
* It adds a copy of the sequence to the table of atoms, if necessary, and | ||
* returns the pointer to that atom. | ||
* | ||
* Never returns null pointer. | ||
* | ||
* @param str sequence of bytes, shall not be null pointer. | ||
* @param len number of bytes | ||
* @return the atom, which is a pointer to the copy of the sequence in the atom | ||
* table. | ||
*/ | ||
const char* atom_new(const char* str, size_t len); | ||
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/** | ||
* Like |atom_new|, it caters to the common use of character strings as atoms. | ||
* | ||
* Adds a copy of that string to the atom table, if necessary, and returns the | ||
* pointer to that atom. | ||
* @param str null-terminated string | ||
* @return the atom, which is a pointer to the copy of the sequence in the atom | ||
* table. | ||
*/ | ||
const char* atom_string(const char* str); | ||
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/** | ||
* Returns the atom for the string representation of the integer |n|. | ||
* @param n integer value to be represented as string. | ||
* @return the atom, which is a pointer to the copy of the integer in the atom | ||
* table. | ||
*/ | ||
const char* atom_int(int64_t n); | ||
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/** | ||
* Returns length of its atom argument. | ||
* | ||
* Will raise error if |str| is not a pointer to an atom. | ||
* | ||
* @param str pointer to an atom. | ||
* @return the string length of an atom. | ||
*/ | ||
size_t atom_length(const char* str); | ||
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#endif // CII_ATOM_H_ |
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// Copyright (c) 2023 Xu Shaohua <[email protected]>. All rights reserved. | ||
// Use of this source is governed by GNU General Public License | ||
// that can be found in the LICENSE file. | ||
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#include "cii/atom.h" | ||
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#include <assert.h> | ||
#include <limits.h> | ||
#include <string.h> | ||
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struct atom_s { | ||
struct atom_s* link; | ||
size_t len; | ||
char* str; | ||
}; | ||
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typedef struct atom_s atom_t; | ||
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const size_t kBucketCap = 2048; | ||
static atom_t g_buckets[kBucketCap]; | ||
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const char* atom_string(const char* str) { | ||
assert(str != NULL); | ||
return atom_new(str, strlen(str)); | ||
} | ||
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const char* atom_int(int64_t n) { | ||
uint64_t m; | ||
if (n == INT64_MIN) { | ||
m = INT64_MAX + 1UL; | ||
} else if (n < 0) { | ||
m = -n; | ||
} else { | ||
m = n; | ||
} | ||
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// 43 characters can hold decimal representation of 128-bit integers. | ||
const size_t kBufLen = 43; | ||
char buf[kBufLen]; | ||
char* end_buf = buf + kBufLen; | ||
char* s = end_buf; | ||
while (m > 0) { | ||
s -= 1; | ||
*s = m % 10 + '0'; | ||
m /= 10; | ||
} | ||
if (n < 0) { | ||
s -= 1; | ||
*s = '-'; | ||
} | ||
assert(s >= buf); | ||
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return atom_new(s, end_buf - s); | ||
} | ||
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