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fizzbuzz.c
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fizzbuzz.c
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#include <string.h>
#include <stdint.h>
#include <unistd.h>
#define STDOUT_BUFFER_SIZE 65536
#define STDOUT_FD 1
static int increment_number(char * number, int number_length) {
number[number_length - 1] = '0';
for (int i = number_length - 2; i >= 0; i--) {
if (number[i] < '9') {
number[i]++;
return 0;
}
number[i] = '0';
}
for (int i = number_length; i > 0; i--) {
number[i] = number[i - 1];
}
number[0] = '1';
return 1;
}
static void loop() {
char buffer[1 << 19] = "1\n2\nFizz\n4\nBuzz\nFizz\n7\n8\nFizz\nBuzz\n11\nFizz\n13\n14\nFizzBuzz\n16\n17\nFizz\n19\nBuzz\nFizz\n22\n23\nFizz\nBuzz\n26\nFizz\n28\n29\nFizzBuzz\n";
char number[64] = "31";
int number_length = 2;
char * ptr_buffer = &buffer[strlen(buffer)];
char * ptr_number = &number[number_length - 1];
while (1) {
#define BUFFER_WRITE_NUMBER() \
__builtin_memcpy(ptr_buffer, number, number_length); \
ptr_buffer += number_length; \
*ptr_buffer = '\n'; \
ptr_buffer++; \
*ptr_number += 1;
#define BUFFER_WRITE_TWO_NUMBERS() \
__builtin_memcpy(ptr_buffer, number, number_length - 1); \
__builtin_memcpy(ptr_buffer + 1 + number_length, number, number_length - 1); \
\
ptr_buffer += number_length; \
*(ptr_buffer - 1) = number[number_length - 1]; \
*ptr_buffer = '\n'; \
ptr_buffer++; \
*ptr_number += 1; \
\
ptr_buffer += number_length; \
*(ptr_buffer - 1) = number[number_length -1]; \
*ptr_buffer = '\n'; \
ptr_buffer++; \
*ptr_number += 1;
#define BUFFER_WRITE_FIZZ() \
__builtin_memcpy(ptr_buffer, "Fizz\n", 5); \
ptr_buffer += 5; \
*ptr_number += 1;
#define BUFFER_WRITE_FIZZBUZZ() \
__builtin_memcpy(ptr_buffer, "FizzBuzz\n", 9); \
ptr_buffer += 9;
#define BUFFER_WRITE_FIZZ_THEN_BUZZ() \
__builtin_memcpy(ptr_buffer, "Fizz\nBuzz\n", 10); \
ptr_buffer += 10;
#define BUFFER_WRITE_BUZZ_THEN_FIZZ() \
__builtin_memcpy(ptr_buffer, "Buzz\nFizz\n", 10); \
ptr_buffer += 10;
#define BUFFER_WRITE_1_TO_10() \
BUFFER_WRITE_TWO_NUMBERS(); \
BUFFER_WRITE_FIZZ(); \
BUFFER_WRITE_NUMBER(); \
BUFFER_WRITE_BUZZ_THEN_FIZZ(); \
*ptr_number += 2; \
BUFFER_WRITE_TWO_NUMBERS(); \
BUFFER_WRITE_FIZZ_THEN_BUZZ(); \
*ptr_number += 1;
#define BUFFER_WRITE_11_TO_21() \
BUFFER_WRITE_NUMBER(); \
BUFFER_WRITE_FIZZ(); \
BUFFER_WRITE_TWO_NUMBERS(); \
BUFFER_WRITE_FIZZBUZZ(); \
*ptr_number += 1; \
BUFFER_WRITE_TWO_NUMBERS(); \
BUFFER_WRITE_FIZZ(); \
BUFFER_WRITE_NUMBER(); \
BUFFER_WRITE_BUZZ_THEN_FIZZ();
#define BUFFER_WRITE_22_TO_30() \
BUFFER_WRITE_TWO_NUMBERS(); \
BUFFER_WRITE_FIZZ_THEN_BUZZ(); \
*ptr_number += 2; \
BUFFER_WRITE_NUMBER(); \
BUFFER_WRITE_FIZZ(); \
BUFFER_WRITE_TWO_NUMBERS(); \
BUFFER_WRITE_FIZZBUZZ();
#define BUFFER_WRITE_30() \
BUFFER_WRITE_1_TO_10(); \
*ptr_number = '1'; \
*(ptr_number - 1) += 1; \
\
BUFFER_WRITE_11_TO_21(); \
*ptr_number = '2'; \
*(ptr_number - 1) += 1; \
\
BUFFER_WRITE_22_TO_30(); \
*ptr_number = '1'; \
*(ptr_number - 1) += 1;
BUFFER_WRITE_30();
BUFFER_WRITE_30();
BUFFER_WRITE_1_TO_10();
// > 99
number_length += increment_number(number, number_length);
ptr_number = &number[number_length - 1];
*ptr_number = '1';
BUFFER_WRITE_11_TO_21();
*ptr_number = '2';
*(ptr_number - 1) += 1;
BUFFER_WRITE_22_TO_30();
*ptr_number = '1';
*(ptr_number - 1) += 1;
BUFFER_WRITE_30();
BUFFER_WRITE_30();
BUFFER_WRITE_1_TO_10();
*ptr_number = '1';
*(ptr_number - 1) += 1;
BUFFER_WRITE_11_TO_21();
// > 99
number_length += increment_number(number, number_length);
ptr_number = &number[number_length - 1];
*ptr_number = '2';
BUFFER_WRITE_22_TO_30();
*ptr_number = '1';
*(ptr_number - 1) += 1;
BUFFER_WRITE_30();
BUFFER_WRITE_30();
BUFFER_WRITE_1_TO_10();
*ptr_number = '1';
*(ptr_number - 1) += 1;
BUFFER_WRITE_11_TO_21();
*ptr_number = '2';
*(ptr_number - 1) += 1;
BUFFER_WRITE_22_TO_30();
// > 99
number_length += increment_number(number, number_length);
ptr_number = &number[number_length - 1];
BUFFER_WRITE_30();
while ((ptr_buffer - buffer) >= STDOUT_BUFFER_SIZE) {
ptr_buffer -= write(STDOUT_FD, buffer, STDOUT_BUFFER_SIZE);
}
}
ptr_buffer -= write(STDOUT_FD, buffer, ptr_buffer - buffer);
}
int main() {
loop();
return 0;
}