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tokenizer.c
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tokenizer.c
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#include "token.h"
static File *current_file;
static char *current_filename;
// temporary in order to test easier
static char *current_input;
// Compilers have to handle multiple input files at the same time
static File **input_files;
void error(char *fmt, ...) {
va_list argument_pointer;
va_start(argument_pointer, fmt);
vfprintf(stderr, fmt, argument_pointer);
fprintf(stderr, "\n");
va_end(argument_pointer);
exit(1);
}
// Reports error message in following format
//
// main.c:10: x = y + 1;
// ^ <error message here>
void verror_at(int line_num, char *location, char *fmt, va_list argument_pointer) {
// Find a line containing `location`
char *line = location;
while (current_input < line && line[-1] != '\n')
line--;
char *end = location;
while (*end != '\n')
end++;
// Print out the line
int indent = fprintf(stderr, "%s:%d: ", current_filename, line_num);
fprintf(stderr, "%.*s\n", (int) (end - line), line);
// Show error message
int position = location - line + indent;
fprintf(stderr, "%*s", position, "");
fprintf(stderr, "^ ");
vfprintf(stderr, fmt, argument_pointer);
fprintf(stderr, "\n");
va_end(argument_pointer);
}
void error_at(char *location, char *fmt, ...) {
int line_num = 1;
for (char *p = current_input; p < location; p++)
if (*p == '\n')
line_num++;
va_list argument_pointer;
va_start(argument_pointer, fmt);
verror_at(line_num, location, fmt, argument_pointer);
exit(1);
}
void error_tok(Token *token, char *fmt, ...) {
va_list argument_pointer;
va_start(argument_pointer, fmt);
verror_at(token->line_num, token->loc, fmt, argument_pointer);
exit(1);
}
static void add_line_numbers(Token *token) {
char *p = current_input;
int n = 1;
do {
if (p == token->loc) {
token->line_num = n;
token = token->next;
}
if (*p == '\n')
n++;
} while(*p++);
}
void free_token(Token *token) {
if (!token) return;
free_token(token->next);
free(token);
}
bool equal(Token *token, char *op) {
return memcmp(token->loc, op, token->len) == 0 && op[token->len] == '\0';
}
Token *skip(Token *token, char *s) {
if (!equal(token, s))
error_tok(token, "expected '%s'", s);
return token->next;
}
bool consume(Token **rest, Token *token, char *str) {
if (equal(token, str)) {
*rest = token->next;
return true;
}
*rest = token;
return false;
}
static Token *new_token(TokenType type, char *start, char *end) {
Token *token = calloc(1, sizeof(Token));
if (token == NULL) {
error("not enough memory in system");
}
token->token_type = type;
token->loc = start;
token->len = end - start;
return token;
}
static bool startswith(char *p, char *q) {
return strncmp(p, q, strlen(q)) == 0;
}
// Returns true if c is valid as the first character of an identifier
static bool is_valid_ident_first_character(char c) {
return ('a' <= c && c <= 'z') || ('A' <= c && c <= 'Z') || c == '_';
}
// Returns true if c is valid as a non-first character of an identifier
static bool is_valid_ident_character(char c) {
return is_valid_ident_first_character(c) || ('0' <= c && c <= '9');
}
static int from_hex(char c) {
if ('0' <= c && c <= '9')
return c - '0';
if ('a' <= c && c <= 'f')
return c - 'a' + 10;
return c - 'A' + 10;
}
// Returns length of punctuator token from p
static int get_punct_length(char *p) {
static char *puncts[] = {
"==", "!=", "<=", ">=", "->", "+=", "-=", "*=", "/=", "++", "--",
"%=", "&=", "|=", "^=", "&&", "||",
};
for (int i = 0; i < sizeof(puncts) / sizeof(*puncts); i++)
if (startswith(p, puncts[i]))
return strlen(puncts[i]);
return ispunct(*p) ? 1 : 0;
}
static bool is_keyword(Token *token) {
static char *keywords[] = {
"return", "if", "else", "for", "while", "int", "sizeof", "char",
"struct", "union", "short", "long", "void", "typedef", "_Bool",
"enum", "static",
};
for (int i = 0; i < sizeof(keywords) / sizeof(*keywords); i++) {
if (equal(token, keywords[i]))
return true;
}
return false;
}
static int read_escaped_char(char **new_pos, char *p) {
if ('0' <= *p && *p <= '7') {
// octal num
int c = *p++ - '0';
if ('0' <= *p && *p <= '7') {
c = (c << 3) + (*p++ - '0');
if ('0' <= *p && *p <= '7')
c = (c << 3) + (*p++ - '0');
}
*new_pos = p;
return c;
}
if (*p == 'x') {
// hex num
p++;
if (!isxdigit(*p))
error_at(p, "invalid hex escape sequence");
int c = 0;
for (; isxdigit(*p); p++)
c = (c << 4) + from_hex(*p);
*new_pos = p;
return c;
}
*new_pos = p + 1;
// Escape sequences are defined using themselves here
// Ex. '\n' is implemented using '\n'. This works
// because the compiler that compiles our compiler knows
// what '\n' is. Basically we inherit the ASCII code of
// '\n' from the compiler that compiles our compiler
// so we don't have to implement the actual code here
// This is for security reasons.
// For more info, read "Reflections on Trusting Trust" by Ken Thompson.
// https://www.cs.cmu.edu/~rdriley/487/papers/Thompson_1984_ReflectionsonTrustingTrust.pdf
switch (*p) {
case 'a': return '\a';
case 'b': return '\b';
case 't': return '\t';
case 'n': return '\n';
case 'v': return '\v';
case 'f': return '\f';
case 'r': return '\r';
// [GNU] \e for the ASCII escape character is a GNU C extension
case 'e': return 27;
default: return *p;
}
}
// Find a closing double-quote.
static char *string_literal_end(char *p) {
char *start = p;
for (; *p != '"'; p++) {
if (*p == '\n' || *p == '\0')
error_at(start, "unclosed string literal");
if (*p == '\\')
p++;
}
return p;
}
static Token *read_string_literal(char *start) {
char *end = string_literal_end(start + 1);
char *buf = calloc(1, end - start);
int len = 0;
for (char *p = start + 1; p < end;) {
if (*p == '\\') {
buf[len++] = read_escaped_char(&p, p + 1);
} else {
buf[len++] = *p++;
}
}
Token *token = new_token(T_STR, start, end + 1);
token->type = array_of(ty_char, len + 1);
token->str = buf;
return token;
}
static Token *read_char_literal(char *start) {
char *p = start + 1;
if (*p == '\0')
error_at(start, "unclosed char literal");
char c;
if (*p == '\\')
c = read_escaped_char(&p, p + 1);
else
c = *p++;
char *end = strchr(p, '\'');
if (!end)
error_at(p, "unclosed char literal");
Token *token = new_token(T_NUM, start, end + 1);
token->val = c;
return token;
}
static Token *read_int_literal(char *start) {
char *p = start;
int base = 10;
if(!strncasecmp(p, "0x", 2) && isalnum(p[2])) {
p += 2;
base = 16;
} else if (!strncasecmp(p, "0b", 2) && isalnum(p[2])) {
p += 2;
base = 2;
} else if (*p == '0') {
base = 8;
}
long val = strtoul(p, &p, base);
if (isalnum(*p))
error_at(p, "invalid digit");
Token *token = new_token(T_NUM, start, p);
token->val = val;
return token;
}
static void identify_keywords(Token *token) {
for (Token *curr = token; curr->token_type != T_EOF; curr = curr->next)
if (is_keyword(curr))
curr->token_type = T_KEYWORD;
}
// Tokenize 'current_file' and returns new tokens
static Token *tokenize(char *filename, char *p) {
current_filename = filename;
current_input = p;
Token head = {};
Token *cur = &head;
while (*p) {
// Skip line comments
if (startswith(p, "//")) {
p += 2;
while (*p != '\n')
p++;
continue;
}
// Skip block comments
if (startswith(p, "/*")) {
char *substring = strstr(p + 2, "*/");
if (!substring)
error_at(p, "unclosed block comment");
p = substring + 2;
continue;
}
// Skip whitespace characters
if (isspace(*p)) {
p++;
continue;
}
// Numeric literal
if (isdigit(*p)) {
cur = cur->next = read_int_literal(p);
p += cur->len;
continue;
}
// String literal
if (*p == '"') {
cur = cur->next = read_string_literal(p);
p += cur->len;
continue;
}
// Character literal
if (*p == '\'') {
cur = cur->next = read_char_literal(p);
p += cur->len;
continue;
}
// Identifier or keyword
if (is_valid_ident_first_character(*p)) {
char *start = p;
do {
p++;
} while (is_valid_ident_character(*p));
cur = cur->next = new_token(T_IDENT, start, p);
continue;
}
// Punctuator
int punct_len = get_punct_length(p);
if (punct_len) {
cur = cur->next = new_token(T_PUNCT, p, p + punct_len);
p += punct_len;
continue;
}
error_at(p, "invalid token");
}
cur = cur->next = new_token(T_EOF, p, p);
add_line_numbers(head.next);
identify_keywords(head.next);
return head.next;
}
File *new_file(char* name, int file_num, char *contents) {
File *file = calloc(1, sizeof(File));
file->name = name;
file->unique_id = file_num;
file->display_name = name;
file->contents = contents;
return file;
}
static char *read_file(char* path) {
FILE *file_path;
if (strcmp(path, "-") == 0) {
// If a given file name is "-", read from stdin
// Source: https://github.com/nektos/act/issues/998
file_path = stdin;
} else {
file_path = fopen(path, "r");
if (file_path == NULL) return NULL;
}
char *buf;
size_t buflen;
FILE *out = open_memstream(&buf, &buflen);
for (;;) {
// https://stackoverflow.com/questions/3033771/file-i-o-with-streams-best-memory-buffer-size
char buf2[4096];
int num_full_items = fread(buf2, sizeof(char), sizeof(buf2), file_path);
if (num_full_items == 0)
break;
fwrite(buf2, sizeof(char), num_full_items, out);
}
if (file_path != stdin)
fclose(file_path);
// Last line should end with '\n'
fflush(out);
if (buflen == 0 || buf[buflen - 1] != '\n') {
fputc('\n', out);
}
fputc('\0', out);
fclose(out);
return buf;
}
Token *tokenize_file(char *path) {
char *p = read_file(path);
if (!p) return NULL;
// UTF-8 text might have a 3-byte long BOM: https://en.wikipedia.org/wiki/Byte_order_mark#Byte-order_marks_by_encoding
// This statement skips it
if (!memcmp(p, "\xef\xbb\xbf", 3))
p += 3;
/*static int file_num;
File* file = new_file(path, file_num + 1, p);
DONT USE THIS CODE RN ITS BROKEN
input_files = realloc(input_files, sizeof(char *) * (file_num + 2));
input_files[file_num] = file;
input_files[file_num + 1] = NULL;
file_num++;*/
return tokenize(path, p);
}