1 files changed, 104 insertions, 0 deletions
diff --git a/21sh/ll-expr/src/lexer/lexer.c b/21sh/ll-expr/src/lexer/lexer.c
new file mode 100644
index 0000000..3b3d29f
--- /dev/null
+++ b/21sh/ll-expr/src/lexer/lexer.c
@@ -0,0 +1,104 @@
+#include "lexer.h"
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+struct lexer *lexer_new(const char *input)
+{
+    struct lexer *new = malloc(sizeof(struct lexer));
+    new->input = input;
+    new->pos = 0;
+    return new;
+}
+
+void lexer_free(struct lexer *lexer)
+{
+    free(lexer);
+}
+
+struct template
+{
+    char value;
+    enum token_type type;
+};
+
+struct template templates[] = {
+    { '+', TOKEN_PLUS }, { '-', TOKEN_MINUS },    { '*', TOKEN_MUL },
+    { '/', TOKEN_DIV },  { '(', TOKEN_LEFT_PAR }, { ')', TOKEN_RIGHT_PAR },
+    { '\0', TOKEN_EOF }, { 0, TOKEN_ERROR }
+};
+
+static ssize_t parse_number(struct lexer *l)
+{
+    union
+    {
+        const char *cc;
+        char *c;
+    } cast;
+    cast.cc = l->input + l->pos;
+    char *in = cast.c;
+    size_t t = 0;
+    while (in[t] && in[t] >= '0' && in[t] <= '9')
+        t++;
+    char tmp = in[t];
+    in[t] = '\0';
+    ssize_t res = atoi(in);
+    in[t] = tmp;
+    return res;
+}
+
+struct token lexer_next_token(struct lexer *lexer)
+{
+    for (; lexer->input[lexer->pos] && lexer->input[lexer->pos] == ' ';
+         lexer->pos++)
+        continue;
+    for (int i = 0; i < 7; i++)
+    {
+        if (lexer->input[lexer->pos] == templates[i].value)
+        {
+            lexer->current_tok.type = templates[i].type;
+            return lexer->current_tok;
+        }
+    }
+    if (lexer->input[lexer->pos] > '9' || lexer->input[lexer->pos] < '0')
+    {
+        lexer->current_tok.type = TOKEN_ERROR;
+        fprintf(stderr, "lexer: invalid token %c\n", lexer->input[lexer->pos]);
+        return lexer->current_tok;
+    }
+    else
+    {
+        lexer->current_tok.type = TOKEN_NUMBER;
+        lexer->current_tok.value = parse_number(lexer);
+        return lexer->current_tok;
+    }
+}
+
+struct token lexer_peek(struct lexer *lexer)
+{
+    return lexer_next_token(lexer);
+}
+
+static size_t count_numbers(ssize_t value)
+{
+    if (value == 0)
+        return 1;
+    size_t size = 0;
+    while (value)
+    {
+        size++;
+        value /= 10;
+    }
+    return size;
+}
+
+struct token lexer_pop(struct lexer *lexer)
+{
+    struct token res = lexer_next_token(lexer);
+    if (res.type == TOKEN_NUMBER)
+        lexer->pos += count_numbers(res.value);
+    else
+        lexer->pos++;
+    return res;
+}