Nelze vybrat více než 25 témat
Téma musí začínat písmenem nebo číslem, může obsahovat pomlčky („-“) a může být dlouhé až 35 znaků.
166 řádky
4.2 KiB
166 řádky
4.2 KiB
#include <stdbool.h>
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#include <sysexits.h>
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#include <assert.h>
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#include <gc.h> // NEVER, EVER HAVE TO CALL FREE (EVER) AGAIN (YES, REALLY)
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#define malloc(n) GC_MALLOC(n)
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#define realloc(o, n) GC_REALLOC(o, n)
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typedef enum { Undefined, Integer, Symbol } type_t;
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union object;
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typedef union object *oop;
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struct Undefined {
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type_t type;
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};
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struct Integer {
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type_t type;
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int value;
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};
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struct Symbol {
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type_t type;
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char *name;
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# if defined(SYMBOL_PAYLOAD)
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SYMBOL_PAYLOAD;
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# endif // defined(SYMBOL_PAYLOAD)
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};
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union object {
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type_t type;
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struct Undefined Undefined;
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struct Integer Integer;
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struct Symbol Symbol;
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};
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union object _null = { .Undefined = { Undefined } };
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oop null = &_null;
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type_t getType(oop ptr) {
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assert(ptr);
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return ptr->type;
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}
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int is(type_t type, oop obj) {
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return type == getType(obj);
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}
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oop _checkType(oop ptr, type_t type) {
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assert(ptr);
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assert(ptr->type == type);
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return ptr;
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}
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// added parens around expansion to protect assignment
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#define get(PTR, TYPE, FIELD) (_checkType(PTR, TYPE)->TYPE.FIELD)
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#define set(PTR, TYPE, FIELD, VALUE) (_checkType(PTR, TYPE)->TYPE.FIELD = VALUE)
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void *memcheck(void *ptr)
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{
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if (NULL == ptr) {
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fprintf(stderr, "Error: out of memory\n");
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exit(EX_OSERR); // this is as close as we have for 'resource unavailable'
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}
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return ptr;
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}
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oop makeInteger(int value) {
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oop newInt = memcheck(malloc(sizeof(union object)));
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newInt->type = Integer;
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newInt->Integer.value = value;
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return newInt;
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}
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oop makeSymbol(char *name) {
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oop newSymb = memcheck(malloc(sizeof(union object)));
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newSymb->type = Symbol;
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newSymb->Symbol.name = name;
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# if defined(SYMBOL_INITIALISE)
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SYMBOL_INITIALISE(newSymb->Symbol);
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# endif // defined(SYMBOL_INITIALISE)
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return newSymb;
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}
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void print(oop ast) {
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assert(ast);
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switch (ast->type) {
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case Undefined:
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printf("null");
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return;
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case Integer:
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printf("%i", get(ast, Integer, value));
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return;
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case Symbol:
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printf("%s=", get(ast, Symbol, name));
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print(get(ast, Symbol, value));
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return;
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}
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assert(0);
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}
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void println(oop ast)
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{
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print(ast);
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printf("\n");
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}
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#define SYMBOL_TABLE_CHUNK 1024
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typedef struct table_t {
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oop *array;
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size_t size;
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size_t capacity;
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} table_t;
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#define TABLE_INITIALISER { NULL, 0, 0 } // first call to table_insert() will initialise storage
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table_t table = TABLE_INITIALISER; // safe but not strictly needed on Unix because BSS segment is initialised to all zeroes
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ssize_t table_search(table_t *table, char *ident)
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{
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assert(table); assert(ident);
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ssize_t l = 0, r = table->size - 1;
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while (l <= r) {
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ssize_t mid = (l + r) / 2;
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int cmpres = strcmp(get(table->array[mid], Symbol, name), ident);
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if (cmpres > 0) r = mid - 1;
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else if (cmpres < 0) l = mid + 1;
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else return mid; // non-negative result => element found at this index
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}
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return -1 - l; // negative result => 'not found', reflected around -1 instead of 0 to allow 'not found' at index 0
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}
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// ssize_t result because -1 means 'error'
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ssize_t table_insert(table_t *table, oop object, size_t pos)
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{
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// Should I use in my code a function starting with _ or is it a convention to prevent its usage ?
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/// You should never really have to use that function except implicitly via get/set.
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/// If you need to insist on a particular type, check it explicitly and produce a real error messge or assertion failure.
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assert(is(Symbol, object));
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if (pos > table->size) { // don't need to check for pos < 0 because size_t is unsigned
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return -1;
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}
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if (table->size >= table->capacity) {
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// on the first call table->array will be NULL and realloc() will behave like malloc()
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table->array = memcheck(realloc(table->array, sizeof(oop) * (table->capacity + SYMBOL_TABLE_CHUNK)));
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table->capacity += SYMBOL_TABLE_CHUNK;
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}
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memmove(table->array + pos + 1, table->array + pos, sizeof(*table->array) * (table->size - pos));
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table->array[pos] = object;
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return ++(table->size);
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}
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oop intern(char *ident)
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{
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ssize_t res= table_search(&table, ident); // < 0 => not found
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if (res >= 0) return table.array[res];
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res= -1 - res; // 'un-negate' the result by reflecting it around X=-1
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oop new_symbol = makeSymbol(memcheck(strdup(ident)));
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table_insert(&table, new_symbol, res);
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return new_symbol;
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}
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