79 lines
1.7 KiB
C
79 lines
1.7 KiB
C
#include "reader.h"
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#include <ctype.h>
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#include <stddef.h>
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static int parse_number(
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memory_pool_t *pool, const char *input, int remaining, expression_t *out)
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{
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(void)pool;
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int value = 0, used = 0;
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while (remaining > 0 && isdigit(*input)) {
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value *= 10;
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value += *input - '0';
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++used;
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--remaining;
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++input;
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}
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out->is_number = true;
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out->number = value;
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return used;
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}
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static int parse_application(
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memory_pool_t *pool, const char *input, int remaining, expression_t *out)
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{
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int result, used = 0;
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expression_t *operand0 = allocate_expression(pool);
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result = parse_number(pool, input, remaining, operand0);
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if (0 == result)
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return 0;
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used += result;
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remaining -= result;
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input += result;
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if (remaining <= 0 || *input != '+')
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return 0;
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++used;
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--remaining;
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++input;
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expression_t *operand1 = allocate_expression(pool);
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result = parse_number(pool, input, remaining, operand1);
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if (0 == result)
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return 0;
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used += result;
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remaining -= result;
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input += result;
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out->is_number = false;
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out->application.operator = OPERATOR_ADD;
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out->application.operands[0] = operand0;
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out->application.operands[1] = operand1;
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return used;
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}
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static int parse_expression(
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memory_pool_t *pool, const char *input, int remaining, expression_t *out)
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{
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int result = parse_application(pool, input, remaining, out);
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if (0 != result)
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return result;
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else
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return parse_number(pool, input, remaining, out);
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}
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const expression_t *
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read_expression(memory_pool_t *pool, const char *input, int len)
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{
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expression_t *expression = allocate_expression(pool);
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if (NULL == expression)
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return NULL;
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parse_expression(pool, input, len, expression);
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return expression;
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}
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