commit ddb7c33c374e12d659f3af2be1ff153f93ba030e
Author: Ole Morud <ole.morud@gmail.com>
Date:   Thu Jan 4 15:13:02 2024 +0100

    Initial commit

diff --git a/src/Makefile b/src/Makefile
new file mode 100644
index 0000000..32081b1
--- /dev/null
+++ b/src/Makefile
@@ -0,0 +1,3 @@
+
+all:
+	gcc -o lang parser.c tokenizer.c error.c file_stream.c
diff --git a/src/error.c b/src/error.c
new file mode 100644
index 0000000..a49f3ca
--- /dev/null
+++ b/src/error.c
@@ -0,0 +1,95 @@
+
+#include "error.h"
+#include <ctype.h>
+#include <stdarg.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+bool error_empty(Error* err)
+{
+    if (!err)
+        return false;
+    return err->msg == NULL;
+}
+
+void error_push(Error* err, const char* fmt, ...)
+{
+	if (!err)
+		return;
+
+	#define MSG_SIZE 128
+
+    // first list element is a dummy element
+    if (err->msg == NULL) {
+        err->msg = malloc(sizeof *err->msg);
+        if (!(err->msg)) {
+            perror("malloc");
+            exit(EXIT_FAILURE);
+        }
+    }
+
+    struct error_msg* m = err->msg;
+
+	while (m->next) {
+		m = m->next;
+	}
+	m->next = malloc(sizeof *m);
+	if (m->next == NULL) {
+		perror("malloc");
+        exit(EXIT_FAILURE);
+	}
+	m->next->message = malloc(MSG_SIZE);
+	if (!(m->next->message)) {
+		perror("malloc");
+        exit(EXIT_FAILURE);
+	}
+	va_list args;
+	va_start(args, fmt);
+	vsnprintf(m->next->message, MSG_SIZE, fmt, args);
+	va_end(args);
+
+	#undef MSG_SIZE
+}
+
+static void error_msg_print(struct error_msg* msg, bool print_colon)
+{
+	if (!msg)
+		return;
+    error_msg_print(msg->next, true);
+	fprintf(stderr, "%s", msg->message);
+    if (print_colon) {
+        fprintf(stderr, ": ");
+    }
+}
+
+void error_print(Error* err)
+{
+    if (!err) {
+        fprintf(stderr, "(empty error)\n");
+        return;
+    }
+    error_msg_print(err->msg, false);
+    fprintf(stderr, "\n");
+}
+
+static void error_msg_free(struct error_msg* msg)
+{
+    if (!msg)
+        return;
+    error_msg_free(msg->next);
+    free(msg->message);
+    free(msg);
+    msg->message = NULL;
+    msg->next    = NULL;
+}
+
+void error_clear(Error* err)
+{
+    if (!err)
+        return;
+
+    error_msg_free(err->msg);
+    err->msg = NULL;
+}
+
diff --git a/src/error.h b/src/error.h
new file mode 100644
index 0000000..01b9d87
--- /dev/null
+++ b/src/error.h
@@ -0,0 +1,28 @@
+
+#pragma once
+
+#include <stddef.h>
+#include <stdbool.h>
+
+struct error_msg {
+	struct error_msg* next;
+	char* message;
+};
+
+typedef struct error {
+    struct error_msg* msg;
+} Error;
+
+/* Returns true if there is no error */
+bool error_empty(Error* err);
+
+/* Add message to error */
+void error_push(Error* err, const char* fmt, ...);
+
+/* Print error */
+void error_print(Error* err);
+
+/* Frees the internal data structures but leaves err in a usable state  */
+void error_clear(Error* err);
+
+#define ERROR_INIT {.msg = NULL}
diff --git a/src/file_stream.c b/src/file_stream.c
new file mode 100644
index 0000000..13c3e07
--- /dev/null
+++ b/src/file_stream.c
@@ -0,0 +1,110 @@
+
+#include <errno.h>
+#include <fcntl.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/mman.h>
+#include <sys/stat.h>
+#include <unistd.h>
+
+#include "error.h"
+#include "file_stream.h"
+
+char* mfile_overflow_slope = NULL;
+
+Mfile* mfile_open(Error* err, char* filename)
+{
+	Mfile* s = malloc(sizeof *s);
+	if (!s) {
+		error_push(err, "failed to allocate file stream struct: %s", strerror(errno));
+        goto malloc_fail;
+	}
+
+	s->fd = open(filename, O_RDONLY);
+	if (s->fd == -1) {
+		error_push(err, "failed to open file %s: %s", filename, strerror(errno));
+        goto open_fail;
+	}
+
+	struct stat sb;
+	int ok = fstat(s->fd, &sb);
+	if (ok == -1) {
+		error_push(err, "failed to stat file %s: %s", filename, strerror(errno));
+        goto stat_fail;
+	}
+	s->size = sb.st_size;
+
+	s->data = mmap(NULL, s->size, PROT_READ, MAP_PRIVATE, s->fd, 0);
+	if (s->data == MAP_FAILED) {
+		error_push(err, "failed to mmap file: %s", strerror(errno));
+        goto mmap_fail;
+	}
+
+    return s;
+
+mmap_fail:
+stat_fail:
+    close(s->fd);
+open_fail:
+    free(s);
+malloc_fail:
+    return NULL;
+}
+
+void mfile_close(Error* err, Mfile* s)
+{
+    int ok;
+    ok = munmap(s->data, s->size);
+    if (ok == -1) {
+        error_push(err, "failed to munmap file: %s", strerror(errno));
+        free(s);
+        return;
+    }
+    close(s->fd);
+    if (ok == -1) {
+        error_push(err, "failed to close file: %s", strerror(errno));
+        free(s);
+        return;
+    }
+    free(s);
+}
+
+int mfile_get(Mfile* s)
+{
+    if (s->pos >= s->size) {
+        return EOF;
+    }
+    return s->data[s->pos++];
+}
+
+bool mfile_eof(Mfile* s)
+{
+    return s->pos >= s->size;
+}
+
+char* mfile_cur(Mfile* s)
+{
+    if (s->pos >= s->size) {
+        return mfile_overflow_slope;
+    }
+    return s->data + s->pos;
+}
+
+int mfile_curchar(Mfile* s)
+{
+    if (s->pos >= s->size) {
+        return EOF;
+    }
+    return *(s->data + s->pos);
+}
+
+void mfile_skip(Mfile* s, int (*f)(int))
+{
+    while (f(*(s->data + s->pos)))
+        s->pos += 1;
+}
+
+
+
+
diff --git a/src/file_stream.h b/src/file_stream.h
new file mode 100644
index 0000000..38b8fae
--- /dev/null
+++ b/src/file_stream.h
@@ -0,0 +1,39 @@
+#pragma once
+
+#include <sys/stat.h>
+#include <stdlib.h>
+#include "error.h"
+
+extern char* mfile_overflow_slope;
+
+typedef struct mfile {
+	char* data;
+	off_t size;
+	size_t pos;
+
+    // internal
+    int fd;
+    struct stat sb;
+    #define mfile_size sb.st_size
+} Mfile;
+
+/* Open memory mapped file */
+Mfile* mfile_open(Error* err, char* filename);
+
+/* Close memory mapped file */
+void mfile_close(Error* err, Mfile* s);
+
+/* Get next byte, returns EOF if end of file */
+int mfile_get(Mfile* s);
+
+/* Returns true if end of file */
+bool mfile_eof(Mfile* s);
+
+/* Returns current position */
+char* mfile_cur(Mfile* s);
+
+/* Skips char until f is false */
+void mfile_skip(Mfile* s, int (*f)(int));
+
+/* Get current char */
+int mfile_curchar(Mfile* s);
diff --git a/src/parser.c b/src/parser.c
new file mode 100644
index 0000000..574da0c
--- /dev/null
+++ b/src/parser.c
@@ -0,0 +1,189 @@
+
+#include "error.h"
+#include "file_stream.h"
+#include "tokenizer.h"
+#include "printable.h"
+
+#include <ctype.h>
+#include <limits.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <sys/mman.h>
+#include <unistd.h>
+#include <string.h>
+#include <errno.h>
+
+/* ======= Grammar Rules =======
+
+statement:
+    : statements statement
+    | statement;
+statement
+    | expr
+expr
+    : INT OPERATOR INT     {$$ = binary_op_int($1, $3, $2);}
+    | INT OPERATOR FLOAT   {conv($1); $$ = binary_op_float($1, $3, $2);}
+    | FLOAT OPERATOR INT   {conv($2); $$ = binary_op_float($1, $3, $2);}
+    | FLOAT OPERATOR FLOAT {$$ = binary_op_float($1, $3, $2);}
+    ;
+   ============================= */
+
+enum value_type {
+	VALUE_INTEGER,
+	VALUE_OPERATOR,
+	VALUE_TYPE_COUNT,
+};
+
+static const char* value_type_str[VALUE_TYPE_COUNT] = {
+	[VALUE_INTEGER] = "VALUE_INTEGER",
+	[VALUE_OPERATOR] = "VALUE_OPERATOR",
+};
+
+typedef struct value {
+	const char* debug_name;
+	enum value_type type;
+	union {
+		int64_t i;
+		char op[3];
+	};
+} Value;
+
+typedef struct symbol_table_entry {
+    const char* debug_name;
+	int id;
+    Value* val;
+    struct symbol_table_entry* next;
+} Symbol_table_entry;
+
+typedef struct symbol_table {
+    Symbol_table_entry* syms;
+} Symbol_table;
+
+static Value* parse_int(Error* err, Token* t)
+{
+	if (t->type != TOKEN_INTEGER) {
+		error_push(err, "%s: unexpected token type: %s", __func__, token_type_str[t->type]);
+		return NULL;
+	}
+	Value* v = malloc(sizeof *v);
+	if (!v) {
+		error_push(err, "%s: failed to allocate value: %s", __func__, strerror(errno));
+		return NULL;
+	}
+	v->type = VALUE_INTEGER;
+	v->i = strtol(t->start, NULL, 10);
+	return v;
+}
+
+static Value* parse_binary_expr(Error* err, Value* lval, Value* rval, Value* op)
+{
+	if (lval->type != VALUE_INTEGER
+	 || rval->type != VALUE_INTEGER
+	 || op->type   != VALUE_OPERATOR)
+	{
+		error_push(err, "%s: unexpected token types: %s %s %s",
+				__func__, value_type_str[lval->type],
+				value_type_str[rval->type], value_type_str[op->type]);
+		return NULL;
+	}
+
+	Value* result = malloc(sizeof *result);
+	if (!result) {
+		error_push(err, "%s: failed to allocate value: %s", __func__, strerror(errno));
+		return NULL;
+	}
+	result->type = VALUE_INTEGER;
+	switch (op->op[0]) {
+	case '+':
+		result->i = lval->i + rval->i;
+		break;
+	case '*':
+		result->i = lval->i * rval->i;
+		break;
+	case '-':
+		result->i = lval->i - rval->i;
+		break;
+	case '/':
+		result->i = lval->i / rval->i;
+		break;
+	}
+	printf("\nCALCULATED EXPRESSION %ld %c %ld = %ld\n", lval->i, op->op[0], rval->i, result->i);
+	return result;
+}
+
+static int parser_next(Error* err, Mfile* m)
+{
+	mfile_skip(m, isspace);
+	Token* t = token_read(err, m);
+	if (t->type == EOF) {
+		return EOF;
+	} else if (!error_empty(err)) {
+		error_print(err);
+		return EOF;
+	} else {
+		fprintf(stderr, "unknown error\n");
+		return EOF;
+	}
+
+	Value* v;
+	switch (t->type) {
+		case TOKEN_INTEGER:
+			v = parse_int(err, t);
+			if (!v) {
+				return EOF;
+			}
+			if (!error_empty(err)) {
+				error_print(err);
+				return EOF;
+			}
+			printf("\nINT: %ld\n", v->i);
+			break;
+			
+	}
+	token_print(err, t);
+	return 0;
+}
+
+
+/* ========================================================================= */
+
+int main(int argc, char** argv)
+{
+    int status = EXIT_SUCCESS;
+
+	if (argc != 2) {
+		fprintf(stderr, "usage: %s <file>\n", argv[0]);
+		return EXIT_FAILURE;
+	}
+
+	// create a protected page for debugging purposes
+	size_t pagesize = sysconf(_SC_PAGESIZE);
+    void* protected_page = mmap(NULL, pagesize, PROT_READ | PROT_WRITE, MAP_ANON | MAP_PRIVATE, -1, 0);
+	mfile_overflow_slope = protected_page + 0;
+    mprotect(protected_page, pagesize, PROT_NONE);
+
+    Error err = ERROR_INIT;
+    Mfile* m = mfile_open(&err, argv[1]);
+    if (!error_empty(&err)) {
+        error_push(&err, "mfile_open");
+        error_print(&err);
+        status = EXIT_FAILURE;
+        error_clear(&err);
+    }
+
+    error_clear(&err);
+	while (!mfile_eof(m)) {
+		parser_next(&err, m);
+	}
+
+    error_clear(&err);
+    mfile_close(&err, m);
+    if (!error_empty(&err)) {
+        error_push(&err, "mfile_close");
+        error_print(&err);
+        status = EXIT_FAILURE;
+    }
+
+    return status;
+}
diff --git a/src/printable.h b/src/printable.h
new file mode 100644
index 0000000..bf3bdc6
--- /dev/null
+++ b/src/printable.h
@@ -0,0 +1,91 @@
+
+#pragma once
+
+#ifdef GENERATE_TABLE
+/*
+ Generates table below:
+    cc -DGENERATE_TABLE -xc printable.h -o generate_table \
+        && ./generate_table >> printable.h
+ */
+#include <assert.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <ctype.h>
+
+static int escape(int c) {
+    return c == '"' || c == '\\';
+}
+
+int main() {
+#define MAX_LINE_WIDTH 80
+#define BUF_SZ 16
+#define NULL_STR "\"<NULL>\", "
+#define TAB "    "
+#define printf_assert(...) assert( printf(__VA_ARGS__) > 0)
+    int written = 0;
+    char buf[BUF_SZ];
+    char* fmt;
+
+    printf_assert(
+        "\n// generated by main() in printable.h\n"
+        "\nstatic const char * asdasd_printable[256] = {"
+        "\n" TAB NULL_STR
+    );
+
+    int line_len = sizeof(TAB) + sizeof(NULL_STR) - 1;
+    for (int c = 1; c < 255; c++) {
+        if (isprint(c) && escape(c)) {
+            fmt = "\"\\%c\", ";
+        } else if (isprint(c)) {
+            fmt = "\"%c\", ";
+        } else {
+            fmt = "\"<%02x>\", ";
+        }
+
+        written = snprintf(buf, BUF_SZ, fmt, c);
+        assert( written > 0 && written < BUF_SZ );
+        line_len += written;
+
+        if (line_len > MAX_LINE_WIDTH) {
+            printf_assert("\n" TAB);
+            line_len = sizeof(TAB) + written - 1;
+        }
+
+        printf_assert(buf);
+    }
+    printf_assert("\"<EOF>\"\n\n};");
+    return EXIT_SUCCESS;
+}
+#endif
+
+#define PRINTABLE(ch) asdasd_printable[(unsigned char)(ch)]
+
+// generated by main() in printable.h
+
+static const char * asdasd_printable[256] = {
+    "<NULL>", "<01>", "<02>", "<03>", "<04>", "<05>", "<06>", "<07>", "<08>", 
+    "<09>", "<0a>", "<0b>", "<0c>", "<0d>", "<0e>", "<0f>", "<10>", "<11>", 
+    "<12>", "<13>", "<14>", "<15>", "<16>", "<17>", "<18>", "<19>", "<1a>", 
+    "<1b>", "<1c>", "<1d>", "<1e>", "<1f>", " ", "!", "\"", "#", "$", "%", "&", 
+    "'", "(", ")", "*", "+", ",", "-", ".", "/", "0", "1", "2", "3", "4", "5", 
+    "6", "7", "8", "9", ":", ";", "<", "=", ">", "?", "@", "A", "B", "C", "D", 
+    "E", "F", "G", "H", "I", "J", "K", "L", "M", "N", "O", "P", "Q", "R", "S", 
+    "T", "U", "V", "W", "X", "Y", "Z", "[", "\\", "]", "^", "_", "`", "a", "b", 
+    "c", "d", "e", "f", "g", "h", "i", "j", "k", "l", "m", "n", "o", "p", "q", 
+    "r", "s", "t", "u", "v", "w", "x", "y", "z", "{", "|", "}", "~", "<7f>", 
+    "<80>", "<81>", "<82>", "<83>", "<84>", "<85>", "<86>", "<87>", "<88>", 
+    "<89>", "<8a>", "<8b>", "<8c>", "<8d>", "<8e>", "<8f>", "<90>", "<91>", 
+    "<92>", "<93>", "<94>", "<95>", "<96>", "<97>", "<98>", "<99>", "<9a>", 
+    "<9b>", "<9c>", "<9d>", "<9e>", "<9f>", "<a0>", "<a1>", "<a2>", "<a3>", 
+    "<a4>", "<a5>", "<a6>", "<a7>", "<a8>", "<a9>", "<aa>", "<ab>", "<ac>", 
+    "<ad>", "<ae>", "<af>", "<b0>", "<b1>", "<b2>", "<b3>", "<b4>", "<b5>", 
+    "<b6>", "<b7>", "<b8>", "<b9>", "<ba>", "<bb>", "<bc>", "<bd>", "<be>", 
+    "<bf>", "<c0>", "<c1>", "<c2>", "<c3>", "<c4>", "<c5>", "<c6>", "<c7>", 
+    "<c8>", "<c9>", "<ca>", "<cb>", "<cc>", "<cd>", "<ce>", "<cf>", "<d0>", 
+    "<d1>", "<d2>", "<d3>", "<d4>", "<d5>", "<d6>", "<d7>", "<d8>", "<d9>", 
+    "<da>", "<db>", "<dc>", "<dd>", "<de>", "<df>", "<e0>", "<e1>", "<e2>", 
+    "<e3>", "<e4>", "<e5>", "<e6>", "<e7>", "<e8>", "<e9>", "<ea>", "<eb>", 
+    "<ec>", "<ed>", "<ee>", "<ef>", "<f0>", "<f1>", "<f2>", "<f3>", "<f4>", 
+    "<f5>", "<f6>", "<f7>", "<f8>", "<f9>", "<fa>", "<fb>", "<fc>", "<fd>", 
+    "<fe>", "<EOF>"
+};
diff --git a/src/test/test.txt b/src/test/test.txt
new file mode 100644
index 0000000..525fb6a
--- /dev/null
+++ b/src/test/test.txt
@@ -0,0 +1,3 @@
+The "quick" brown fox jumps at 8.42 m/h over the lazy dog
+
+10 + 20 = 30
diff --git a/src/test/test_error.c b/src/test/test_error.c
new file mode 100644
index 0000000..64aaa4a
--- /dev/null
+++ b/src/test/test_error.c
@@ -0,0 +1,63 @@
+
+#include "error.h"
+#include <stddef.h>
+#include <stdlib.h>
+#include <errno.h>
+#include <string.h>
+#include <stdio.h>
+
+int bad_alloc(struct error* err)
+{
+    void* bad = malloc(9223372036854775807UL);
+    if (!bad) {
+        error_push(err, "bad_alloc failed: malloc: %s", strerror(errno));
+        return -1;
+    }
+    return 0;
+}
+
+int failer(struct error* err)
+{
+    bad_alloc(err);
+    if (!error_empty(err)) {
+        error_push(err, "failer failed");
+        return -1;
+    }
+    return 0;
+}
+
+int winner(struct error* err)
+{
+    return 1;
+}
+
+int main()
+{
+    int status = EXIT_SUCCESS;
+
+    fprintf(stderr, "Running function that results in error\n");
+    struct error err = ERROR_INIT;
+    failer(&err);
+    if (!error_empty(&err)) {
+        fprintf(stderr, "OK\n");
+    } else {
+        fprintf(stderr, "function `failer` did not fail\n");
+        status = EXIT_FAILURE;
+    }
+
+    error_clear(&err);
+
+    fprintf(stderr, "Running function that should not return error\n");
+    winner(&err);
+    if (!error_empty(&err)) {
+        error_print(&err);
+        fprintf(stderr, "function `winner` failed when it's not supposed to");
+        status = EXIT_FAILURE;
+    } else {
+        fprintf(stderr, "OK\n");
+    }
+
+    error_clear(&err);
+
+    return status;
+}
diff --git a/src/test/test_file_stream.c b/src/test/test_file_stream.c
new file mode 100644
index 0000000..2f062d0
--- /dev/null
+++ b/src/test/test_file_stream.c
@@ -0,0 +1,46 @@
+
+#include "file_stream.h"
+#include <string.h>
+#include <stdio.h>
+
+int main(int argc, char** argv)
+{
+    int status = EXIT_SUCCESS;
+
+    fprintf(stderr, "attempting to open test.txt\n");
+    Error err = ERROR_INIT;
+    Mfile* m = mfile_open(&err, "test.txt");
+    if (!error_empty(&err)) {
+        error_push(&err, "mfile_open test failed");
+        error_print(&err);
+        status = EXIT_FAILURE;
+    } else {
+        fprintf(stderr, "OK\n");
+    }
+
+    fprintf(stderr, "attempting to read from test.txt with mfile_get(m)\n");
+    char str[12];
+    size_t n = 0;
+    while (!mfile_eof(m) && n < 12) {
+        str[n++] = mfile_get(m);
+    }
+    if (strncmp("the brown fox", str, n) != 0) {
+        error_push(&err, "mfile_get test failed");
+        error_print(&err);
+        status = EXIT_FAILURE;
+    } else {
+        fprintf(stderr, "OK\n");
+    }
+
+    fprintf(stderr, "attempting to close\n");
+    mfile_close(&err, m);
+    if (!error_empty(&err)) {
+        error_push(&err, "mfile_close test failed");
+        error_print(&err);
+        status = EXIT_FAILURE;
+    } else {
+        fprintf(stderr, "OK\n");
+    }
+
+    return status;
+}
diff --git a/src/test/test_tokenizer.c b/src/test/test_tokenizer.c
new file mode 100644
index 0000000..e987ab4
--- /dev/null
+++ b/src/test/test_tokenizer.c
@@ -0,0 +1,27 @@
+
+#include <stdlib.h>
+#include "error.h"
+#include "file_stream.h"
+
+int main(int argc, char** argv)
+{
+    int status = EXIT_SUCCESS;
+
+    Error err = ERROR_INIT;
+    Mfile* m = mfile_open(&err, "test.txt");
+    if (!error_empty(&err)) {
+        error_push(&err, "mfile_open");
+        error_print(&err);
+        status = EXIT_FAILURE;
+    }
+
+    mfile_close(&err, m);
+    if (!error_empty(&err)) {
+        error_push(&err, "mfile_close");
+        error_print(&err);
+        status = EXIT_FAILURE;
+    }
+
+
+    return status;
+}
diff --git a/src/tokenizer.c b/src/tokenizer.c
new file mode 100644
index 0000000..6decd5a
--- /dev/null
+++ b/src/tokenizer.c
@@ -0,0 +1,170 @@
+
+#include "error.h"
+#include "file_stream.h"
+#include "tokenizer.h"
+#include "printable.h"
+
+#include <ctype.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <math.h>
+#include <stddef.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#define MAX(a, b) ((a) > (b) ? (a) : (b))
+#define MIN(a, b) ((a) < (b) ? (a) : (b))
+
+static const bool is_operator[256] = {
+    ['+'] = 1, ['-'] = 1, ['*'] = 1, ['/'] = 1, ['='] = 1, ['%'] = 1,
+    ['&'] = 1, ['|'] = 1, ['<'] = 1, ['>'] = 1, ['!'] = 1, ['^'] = 1,
+    ['('] = 1, [')'] = 1, ['~'] = 1
+};
+
+static void token_read_operator(Error* err, Mfile* m, Token* t)
+{
+    t->type = TOKEN_OPERATOR;
+    t->start = mfile_cur(m);
+    while (!mfile_eof(m) && is_operator[(unsigned char)mfile_get(m)])
+        /* NOOP */;
+    m->pos -= 1;
+    t->end = mfile_cur(m);
+}
+
+static void token_read_number(Error* err, Mfile* m, Token* t)
+{
+    t->start = mfile_cur(m);
+
+	if (mfile_curchar(m) == '-') {
+		m->pos += 1;
+	}
+
+    mfile_skip(m, isdigit);
+
+    if (mfile_curchar(m) == '.') {
+        t->type = TOKEN_FLOATING;
+        m->pos += 1;
+        mfile_skip(m, isdigit);
+    } else {
+        t->type = TOKEN_INTEGER;
+    }
+    t->end = mfile_cur(m);
+}
+
+int64_t token_eval_int(Error* err, Token* t)
+{
+	char* endptr;
+	int64_t n = strtoll(t->start, &endptr, 10);
+	if (endptr != t->end) {
+		error_push(err, "%s: invalid integer: %s", __func__, t->start);
+		return 0;
+	}
+	return n;
+}
+
+double token_eval_float(Error* err, Token* t)
+{
+	char* endptr;
+	double n = strtod(t->start, &endptr);
+	if (endptr != t->end) {
+		error_push(err, "%s: invalid floating point: %s", __func__, t->start);
+		return 0;
+	}
+	if (n == HUGE_VAL || n == -HUGE_VAL) {
+		error_push(err, "%s: invalid floating point: %s", __func__, t->start);
+	}
+	return n;
+}
+
+static void token_read_string(Error* err, Mfile* m, Token* t)
+{
+    t->type = TOKEN_STRING;
+    t->start = mfile_cur(m);
+
+    m->pos += 1;
+    bool escaped = false;
+    while (!mfile_eof(m) && (mfile_curchar(m) != '"' || escaped)) {
+        escaped = mfile_get(m) == '\\';
+    }
+    if (mfile_curchar(m) != '"') {
+        error_push(err, "%s: expected '\"', got %c", __func__, PRINTABLE(*(mfile_cur(m))));
+        return;
+    }
+    m->pos += 1;
+
+    t->end = mfile_cur(m);
+}
+
+static void token_read_identifier(Error* err, Mfile* m, Token* t)
+{
+    t->type = TOKEN_IDENTIFIER;
+    t->start = mfile_cur(m);
+
+    if (!isalpha(*(t->start))) {
+        error_push(err, "%s, expected identifier, got %c", __func__, PRINTABLE(*(t->start)));
+        return;
+    }
+
+    mfile_skip(m, isalnum);
+
+    t->end = mfile_cur(m);
+
+    return;
+}
+
+static void token_eval_identifier(Token* t)
+{
+	
+}
+
+Token* token_read(Error* err, Mfile* m)
+{
+    Token* t = calloc(1, sizeof *t);
+    if (!t) {
+        error_push(err, "failed to allocate token: %s", strerror(errno));
+        return NULL;
+    }
+    const int c = mfile_curchar(m);
+
+    if (isalpha(c)) {
+        token_read_identifier(err, m, t);
+    } else if (c == '"') {
+        token_read_string(err, m, t);
+    } else if (isdigit(c) || c == '-') {
+        token_read_number(err, m, t);
+    } else if (is_operator[c]) {
+        token_read_operator(err, m, t);
+	} else if ( c == EOF ) {
+		t->type = EOF;
+    } else {
+        error_push(err, "unexpected character: %c", PRINTABLE(c));
+    }
+
+    return t;
+}
+
+void token_print(Error* err, Token* t)
+{
+	int ok;
+    char* start = t->start;
+    ok = fprintf(stderr, "{\n\t\"");
+	if (ok < 0) {
+		error_push(err, "failed to print token: %s", strerror(errno));
+		return;
+	}
+    while (start < t->end) {
+		ok = fputc(*start, stderr);
+		if (ok < 0) {
+			error_push(err, "failed to print token: %s", strerror(errno));
+			return;
+		}
+        start += 1;
+    }
+    ok = fprintf(stderr, "\"\n\ttype: %s\n}\n", token_type_str[t->type]);
+	if (ok < 0) {
+		error_push(err, "failed to print token: %s", strerror(errno));
+		return;
+	}
+}
+
diff --git a/src/tokenizer.h b/src/tokenizer.h
new file mode 100644
index 0000000..2bd2017
--- /dev/null
+++ b/src/tokenizer.h
@@ -0,0 +1,45 @@
+#pragma once
+
+#include "file_stream.h"
+
+#include <stdbool.h>
+#include <stdint.h>
+
+enum token_type {
+    TOKEN_IDENTIFIER = 0, // [a-zA-Z][a-zA-Z0-9_]*
+    TOKEN_STRING     = 1,     // "[^"]*"
+    TOKEN_INTEGER    = 2,    // [0-9]+
+    TOKEN_FLOATING   = 3,   // [0-9]+\.[0-9]*
+    TOKEN_OPERATOR   = 4,   // + - * /
+	TOKEN_EOF        = 5,
+    TOKEN_UNKNOWN    = 6,
+    TOKEN_TYPE_COUNT = 7
+};
+
+static const char* token_type_str[TOKEN_TYPE_COUNT] = {
+    "TOKEN_IDENTIFIER",
+    "TOKEN_STRING",
+    "TOKEN_INTEGER",
+    "TOKEN_FLOATING",
+    "TOKEN_OPERATOR",
+	"TOKEN_EOF",
+    "TOKEN_UNKNOWN",
+};
+
+typedef struct token {
+    char* start;
+    char* end;
+    uint64_t type;
+	union {
+		int64_t i;
+		double  f;
+	} parsed;
+} Token;
+
+Token* token_read(Error* err, Mfile* m);
+void token_print(Error* err, Token* t);
+
+int64_t token_eval_int(Error* err, Token* t);
+double token_eval_float(Error* err, Token* t);
+
+