1 files changed, 86 insertions, 0 deletions
diff --git a/src/lexer.c b/src/lexer.c
new file mode 100644
index 0000000..159f73b
--- /dev/null
+++ b/src/lexer.c
@@ -0,0 +1,86 @@
+#include <stdlib.h>
+#include <stdio.h>
+#include <ctype.h>
+
+#include "utils.h"
+#include "lexer.h"
+#include "types.h"
+
+const char *PIT_LEX_TOKEN_NAMES[PIT_LEX_TOKEN__SENTINEL] = {
+    [PIT_LEX_TOKEN_EOF] = "eof",
+    [PIT_LEX_TOKEN_LPAREN] = "lparen",
+    [PIT_LEX_TOKEN_RPAREN] = "rparen",
+    [PIT_LEX_TOKEN_DOT] = "dot",
+    [PIT_LEX_TOKEN_QUOTE] = "quote",
+    [PIT_LEX_TOKEN_INTEGER_LITERAL] = "integer_literal",
+    [PIT_LEX_TOKEN_STRING_LITERAL] = "string_literal",
+    [PIT_LEX_TOKEN_SYMBOL] = "symbol",
+};
+
+const char *pit_lex_token_name(pit_lex_token t) {
+    return PIT_LEX_TOKEN_NAMES[t];
+}
+
+static bool is_more_input(pit_lexer *st) {
+    return st && st->end < st->len;
+}
+
+static int is_symchar(int c) {
+    return c != '(' && c != ')' && c != '.' && c != '\'' && c != '"' && isprint(c) && !isspace(c);
+}
+
+static char peek(pit_lexer *st) {
+    if (is_more_input(st)) return st->input[st->end];
+    else return 0;
+}
+
+static char advance(pit_lexer *st) {
+    if (is_more_input(st)) return st->input[st->end++];
+    else return 0;
+}
+
+static bool match(pit_lexer *st, int (*f)(int)) {
+    if (f(peek(st))) {
+        st->end += 1;
+        return true;
+    } else return false;
+}
+
+pit_lexer *pit_lex_file(char *path) {
+    pit_lexer *ret = malloc(sizeof(*ret));
+    FILE *f = fopen(path, "r");
+    if (!f) pit_panic("failed to open file for lexing: %s", path);
+    fseek(f, 0, SEEK_END);
+    ret->len = ftell(f);
+    fseek(f, 0, SEEK_SET);
+    ret->input = calloc(ret->len, sizeof(char));
+    fread(ret->input, sizeof(char), ret->len, f);
+    ret->start = 0;
+    ret->end = 0;
+    return ret;
+}
+
+pit_lex_token pit_lex_next(pit_lexer *st) {
+restart:
+    st->start = st->end;
+    char c = advance(st);
+    switch (c) {
+    case 0: return PIT_LEX_TOKEN_EOF;
+    case ';': while (is_more_input(st) && advance(st) != '\n'); goto restart;
+    case '(': return PIT_LEX_TOKEN_LPAREN;
+    case ')': return PIT_LEX_TOKEN_RPAREN;
+    case '.': return PIT_LEX_TOKEN_DOT;
+    case '\'': return PIT_LEX_TOKEN_QUOTE;
+    case '"':
+        while (peek(st) != '"') {
+            if (peek(st) == '\\') advance(st); // skip escaped characters
+            if (!advance(st)) pit_panic("unterminated string starting at: %d", st->start);
+        }
+        advance(st);
+        return PIT_LEX_TOKEN_STRING_LITERAL;
+    default:
+        if (isspace(c)) goto restart;
+        if (isdigit(c)) { while (match(st, isdigit)); return PIT_LEX_TOKEN_INTEGER_LITERAL; }
+        else { while (match(st, is_symchar)); return PIT_LEX_TOKEN_SYMBOL; }
+    }
+}