Initial commit

interpreters/bf.c

@@ -0,0 +1,160 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <stdint.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 *
+xmalloc (size_t n)
+{
+	void *p = malloc (n);
+	if (!p)
+		exit_fatal ("malloc: %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->alloc = 16;
+	self->len = 0;
+	self->str = strcpy (xmalloc (self->alloc), "");
+}
+
+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->len += n;
+	self->str[self->len] = '\0';
+}
+
+static void
+str_append_c (struct str *self, char c)
+{
+	str_append_data (self, &c, 1);
+}
+
+// --- Main --------------------------------------------------------------------
+
+int
+main (int argc, char *argv[])
+{
+	struct str program; str_init (&program);
+	struct str data;    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");
+
+	size_t dataptr = 0;
+	str_append_c (&data, 0);
+
+	for (size_t i = 0; i < program.len; i++)
+	{
+		switch (program.str[i])
+		{
+			long pairs;
+		case '>':
+			assert (dataptr != SIZE_MAX);
+			dataptr++;
+			if (dataptr == data.len)
+				str_append_c (&data, 0);
+			break;
+		case '<':
+			assert (dataptr != 0);
+			dataptr--;
+			break;
+
+		case '+': data.str[dataptr]++; break;
+		case '-': data.str[dataptr]--; break;
+
+		case '.':
+			fputc (data.str[dataptr], stdout);
+			break;
+		case ',':
+			data.str[dataptr] = c = fgetc (input);
+			assert (c != EOF);
+			break;
+
+		case '[':
+			if (data.str[dataptr]) break;
+
+			for (pairs = 0; i < program.len; i++)
+			{
+				switch (program.str[i])
+				{
+				case '[': pairs++; break;
+				case ']': pairs--; break;
+				}
+				if (!pairs)
+					break;
+			}
+			assert (!pairs);
+			break;
+		case ']':
+			if (!data.str[dataptr]) break;
+
+			for (pairs = 0; i != SIZE_MAX; i--)
+			{
+				switch (program.str[i])
+				{
+				case '[': pairs--; break;
+				case ']': pairs++; break;
+				}
+				if (!pairs)
+					break;
+			}
+			assert (!pairs);
+			break;
+		default:
+			break;
+		}
+	}
+	return 0;
+}