asm: lexer implementation.

src/as/lexer.c

@@ -0,0 +1,221 @@
+
+#include <stdio.h>
+#include <string.h>
+#include "lexer.h"
+
+/**
+ * macros for the grammar.
+ */
+
+// Numbers is defined as [0-9]
+#define number(x) ((x) >= '0' && (x) <= '9')
+
+// The first digit can however also contain '-'
+#define first_number(x) (number(x) || (x) == '-' )
+
+// First character in strings can be [a-z][A-Z] or '_'
+#define first_string(x)			\
+	(  ((x) >= 'a' && (x) <= 'z')   \
+	|| ((x) >= 'A' && (x) <= 'Z')	\
+	||  (x) == '_'			)
+
+// All characters after can also include numbers or ':'
+#define string(x) \
+	(first_string(x) || number(x))
+
+#define space(x) ((x) == ' ' || (x) == '\t' || (x) == '\r')
+
+
+/**
+ * Helper functions
+ */
+
+static int read_next(struct lexer *lex) {
+
+ 	int c, comment = 0;
+
+ 	while((c = fgetc(lex->fp)) != EOF) {
+
+ 		if (c == '\n')
+			break;
+
+ 		if (comment)
+ 			continue;
+
+ 		if (c == ';') {
+ 			comment = 1;
+ 		} else if (!space(c)) {
+ 			break;
+ 		}
+ 	}
+ 	return c;
+ }
+
+static int read_number(FILE *fp) {
+
+	int c, neg = 0, val = 0;
+	while((c = fgetc(fp)) != EOF) {
+		if (neg == 0 && c == '-') {
+			neg = 1;
+			continue;
+		}
+		if (!number(c)) {
+			ungetc(c, fp);
+			break;
+		}
+		val = (val * 10) + (c - '0');
+	}
+
+	if (neg)
+		return -1 * val;
+	return val;
+}
+
+static int read_string(FILE *fp) {
+
+	int c, label_decl = 0, i = 0;
+	char buf[64];
+
+	while((c = fgetc(fp)) != EOF && i < 64) {
+
+		if (string(c)) {
+			buf[i++] = c;
+		} else {
+			if (c == ':') {
+				label_decl = 1;
+			} else {
+				ungetc(c, fp);
+			}
+			break;
+		}
+	}
+	buf[i] = '\0';
+
+	if (label_decl) {
+		return TOKEN_LABEL_DECL;
+	} else if (!strcmp("noop", buf)) {
+		return TOKEN_OPCODE_NOOP;
+	} else if (!strcmp("add", buf)) {
+		return TOKEN_OPCODE_ADD;
+	} else if (!strcmp("movl", buf)) {
+		return TOKEN_OPCODE_MOVL;
+	} else if (!strcmp("movh", buf)) {
+		return TOKEN_OPCODE_MOVH;
+	} else if (!strcmp("ld", buf)) {
+		return TOKEN_OPCODE_LD;
+	} else if (!strcmp("sw", buf)) {
+		return TOKEN_OPCODE_SW;
+	} else if (!strcmp("beq", buf)) {
+		return TOKEN_OPCODE_BEQ;
+	} else if (!strcmp("jmp", buf)) {
+		return TOKEN_OPCODE_JMP;
+	} else if (!strcmp("jr", buf)) {
+		return TOKEN_OPCODE_JR;
+	} else if (!strcmp("int", buf)) {
+		return TOKEN_OPCODE_INT;
+	}
+	return TOKEN_LABEL;
+}
+
+/**
+ * Exposed functions
+ */
+
+void lexer_init(struct lexer *lex, FILE *fp) {
+
+	lex->lineno = 1;
+	lex->fp = fp;
+	lex->token.type = TOKEN_EOI;
+}
+
+int lexer_get_next(struct lexer *lex) {
+
+	uint16_t num;
+	int ch = read_next(lex);
+
+	if (lex->token.type == TOKEN_EOL)
+		lex->lineno++;
+
+	switch(ch) {
+	case EOF : lex->token.type = TOKEN_EOI;
+		break;
+	case '\n' :
+		lex->token.type = TOKEN_EOL;
+		break;
+	case ',' : lex->token.type = TOKEN_ARG_SEP;
+		break;
+	case '$' :
+		lex->token.type = TOKEN_REG;
+		num = read_number(lex->fp);
+		// Registers is 8-bit only.
+		if (num > 0xF) {
+			fprintf(stderr, "ERROR: Invalid register value '%i' on line: %i\n", num, lex->lineno);
+			return -1;
+		}
+		lex->token.value.n = num;
+		break;
+	default:
+		if (first_number(ch)) {
+			ungetc(ch, lex->fp);
+			lex->token.type = TOKEN_NUMBER;
+			lex->token.value.n = read_number(lex->fp);
+		} else if (first_string(ch)) {
+			ungetc(ch, lex->fp);
+			lex->token.type = read_string(lex->fp);
+		} else {
+			fprintf(stderr, "ERROR: Invalid character '%c' on line: %i\n", ch, lex->lineno);
+			return -1;
+		}
+	}
+
+	lex->token.lineno = lex->lineno;
+	return 0;
+}
+
+void lexer_print_token(struct token *token) {
+
+	static int lineno = 0;
+
+	if (token->lineno != lineno) {
+		lineno = token->lineno;
+		printf("\n%i: ", lineno);
+	}
+
+	switch(token->type) {
+	case TOKEN_OPCODE_NOOP : printf(" [OP NOOP] ");
+		break;
+	case TOKEN_OPCODE_ADD : printf(" [OP ADD] ");
+		break;
+	case TOKEN_OPCODE_MOVL : printf(" [OP MOVL] ");
+		break;
+	case TOKEN_OPCODE_MOVH : printf(" [OP MOVH] ");
+		break;
+	case TOKEN_OPCODE_LD : printf(" [OP LD] ");
+		break;
+	case TOKEN_OPCODE_SW : printf(" [OP SW] ");
+		break;
+	case TOKEN_OPCODE_BEQ : printf(" [OP BEQ] ");
+		break;
+	case TOKEN_OPCODE_JMP : printf(" [OP JMP] ");
+		break;
+	case TOKEN_OPCODE_JR : printf(" [OP JR] ");
+		break;
+	case TOKEN_OPCODE_INT : printf(" [OP INT] ");
+		break;
+	case TOKEN_LABEL : printf(" [LABEL] ");
+		break;
+	case TOKEN_LABEL_DECL : printf(" [LABEL DECL] ");
+		break;
+	case TOKEN_REG : printf(" [REG %i] ", token->value.n);
+		break;
+	case TOKEN_ARG_SEP : printf(" [SEP] ");
+		break;
+	case TOKEN_NUMBER : printf(" [NUM %i] ", token->value.n);
+		break;
+	case TOKEN_EOI : printf(" [EOI] ");
+		break;
+	case TOKEN_EOL : printf(" [EOL] ");
+		break;
+	default: printf(" [U] ");
+	}
+}