diff options
Diffstat (limited to 'interpreters/bf-optimizing.c')
| -rw-r--r-- | interpreters/bf-optimizing.c | 213 |
1 files changed, 213 insertions, 0 deletions
diff --git a/interpreters/bf-optimizing.c b/interpreters/bf-optimizing.c new file mode 100644 index 0000000..b37c0f2 --- /dev/null +++ b/interpreters/bf-optimizing.c @@ -0,0 +1,213 @@ +#include <stdio.h> +#include <stdlib.h> +#include <string.h> +#include <stdint.h> +#include <stdbool.h> +#include <assert.h> +#include <errno.h> + +#define exit_fatal(...) \ + do { \ + fprintf (stderr, "fatal: " __VA_ARGS__); \ + exit (EXIT_FAILURE); \ + } while (0) + +// --- Safe memory management -------------------------------------------------- + +static void * +xcalloc (size_t m, size_t n) +{ + void *p = calloc (m, n); + if (!p) + exit_fatal ("calloc: %s\n", strerror (errno)); + return p; +} + +static void * +xrealloc (void *o, size_t n) +{ + void *p = realloc (o, n); + if (!p && n) + exit_fatal ("realloc: %s\n", strerror (errno)); + return p; +} + +// --- Dynamically allocated strings ------------------------------------------- + +struct str +{ + char *str; ///< String data, null terminated + size_t alloc; ///< How many bytes are allocated + size_t len; ///< How long the string actually is +}; + +static void +str_init (struct str *self) +{ + self->len = 0; + self->str = xcalloc (1, (self->alloc = 16)); +} + +static void +str_ensure_space (struct str *self, size_t n) +{ + // We allocate at least one more byte for the terminating null character + size_t new_alloc = self->alloc; + while (new_alloc <= self->len + n) + new_alloc <<= 1; + if (new_alloc != self->alloc) + self->str = xrealloc (self->str, (self->alloc = new_alloc)); +} + +static void +str_append_data (struct str *self, const void *data, size_t n) +{ + str_ensure_space (self, n); + memcpy (self->str + self->len, data, n); + self->str[self->len += n] = '\0'; +} + +static void +str_append_c (struct str *self, char c) +{ + str_append_data (self, &c, 1); +} + +// --- Main -------------------------------------------------------------------- + +struct str program; ///< Raw program +struct str data; ///< Data tape + +enum command { RIGHT, LEFT, INC, DEC, SET, IN, OUT, BEGIN, END }; +bool grouped[] = { 1, 1, 1, 1, 1, 0, 0, 0, 0 }; +struct instruction { enum command cmd; size_t arg; }; + +int +main (int argc, char *argv[]) +{ + (void) argc; str_init (&program); + (void) argv; str_init (&data); + + int c; + while ((c = fgetc (stdin)) != EOF) + str_append_c (&program, c); + if (ferror (stdin)) + exit_fatal ("can't read program\n"); + + FILE *input = fopen ("/dev/tty", "rb"); + if (!input) + exit_fatal ("can't open terminal for reading\n"); + +// - - Decode and group - - - - - - - - - - - - - - - - - - - - - - - - - - - - + + struct instruction *parsed = xcalloc (sizeof *parsed, program.len); + size_t parsed_len = 0; + + for (size_t i = 0; i < program.len; i++) + { + enum command cmd; + switch (program.str[i]) + { + case '>': cmd = RIGHT; break; + case '<': cmd = LEFT; break; + case '+': cmd = INC; break; + case '-': cmd = DEC; break; + case '.': cmd = OUT; break; + case ',': cmd = IN; break; + case '[': cmd = BEGIN; break; + case ']': cmd = END; break; + default: continue; + } + + if (!parsed_len || !grouped[cmd] || parsed[parsed_len - 1].cmd != cmd) + parsed_len++; + + parsed[parsed_len - 1].cmd = cmd; + parsed[parsed_len - 1].arg++; + } + +// - - Simple optimization pass - - - - - - - - - - - - - - - - - - - - - - - - + + size_t in = 0, out = 0; + for (; in < parsed_len; in++, out++) + { + if (in + 2 < parsed_len + && parsed[in ].cmd == BEGIN + && parsed[in + 1].cmd == DEC && parsed[in + 1].arg == 1 + && parsed[in + 2].cmd == END) + { + parsed[out].cmd = SET; + parsed[out].arg = 0; + in += 2; + } + else if (out && parsed[out - 1].cmd == SET && parsed[in].cmd == INC) + parsed[--out].arg += parsed[in].arg; + else if (out != in) + parsed[out] = parsed[in]; + } + + parsed_len = out; + +// - - Loop pairing - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - + + size_t nesting = 0; + size_t *stack = xcalloc (sizeof *stack, parsed_len); + for (size_t i = 0; i < parsed_len; i++) + { + switch (parsed[i].cmd) + { + case BEGIN: + stack[nesting++] = i; + break; + case END: + assert (nesting > 0); + + --nesting; + parsed[stack[nesting]].arg = i; + parsed[i].arg = stack[nesting]; + default: + break; + } + } + assert (nesting == 0); + +// - - Runtime - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - + + size_t dataptr = 0; + str_append_c (&data, 0); + + for (size_t i = 0; i < parsed_len; i++) + { + size_t arg = parsed[i].arg; + switch (parsed[i].cmd) + { + case RIGHT: + assert (SIZE_MAX - dataptr > arg); + dataptr += arg; + + while (dataptr >= data.len) + str_append_c (&data, 0); + break; + case LEFT: + assert (dataptr >= arg); + dataptr -= arg; + break; + + case INC: data.str[dataptr] += arg; break; + case DEC: data.str[dataptr] -= arg; break; + case SET: data.str[dataptr] = arg; break; + + case OUT: + fputc (data.str[dataptr], stdout); + break; + case IN: + data.str[dataptr] = c = fgetc (input); + assert (c != EOF); + break; + + case BEGIN: if (!data.str[dataptr]) i = arg; break; + case END: if ( data.str[dataptr]) i = arg; break; + } + } + return 0; +} |