From dbbfac1236ad783ccace11058c972d9eb5ef7c6c Mon Sep 17 00:00:00 2001
From: Aryadev Chavali <aryadev@aryadevchavali.com>
Date: Tue, 24 Oct 2023 18:20:59 +0100
Subject: Wrote lexer for assembly

Pretty simple tokeniser, doesn't do a lot and needs to error check better.
---
 asm/main.c | 154 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++---
 1 file changed, 148 insertions(+), 6 deletions(-)

(limited to 'asm')

diff --git a/asm/main.c b/asm/main.c
index 3f6209b..042850a 100644
--- a/asm/main.c
+++ b/asm/main.c
@@ -10,19 +10,37 @@
  * Description: Assembly source code compiler, targeting OVM
  */
 
+#include <ctype.h>
+#include <stdbool.h>
 #include <stdio.h>
+#include <string.h>
 
 #include <lib/darr.h>
 
 typedef enum TokenType
 {
-  TOKEN_WHITESPACE,
   TOKEN_BYTE_LITERAL,
   TOKEN_HWORD_LITERAL,
   TOKEN_WORD_LITERAL,
   TOKEN_SYMBOL,
 } token_type_t;
 
+const char *token_type_as_cstr(token_type_t type)
+{
+  switch (type)
+  {
+  case TOKEN_BYTE_LITERAL:
+    return "BYTE_LITERAL";
+  case TOKEN_HWORD_LITERAL:
+    return "HWORD_LITERAL";
+  case TOKEN_WORD_LITERAL:
+    return "WORD_LITERAL";
+  case TOKEN_SYMBOL:
+    return "SYMBOL";
+  }
+  return "";
+}
+
 typedef struct
 {
   token_type_t type;
@@ -33,14 +51,138 @@ typedef struct
 // We can use darr_read_file as an in memory buffer of source code
 // Then just create new darr's for tokens, then instructions.  Then
 // emit bytecode in the end.
+typedef darr_t buffer_t;
+
+size_t space_left(buffer_t *buffer)
+{
+  if (buffer->available == buffer->used)
+    return 0;
+  return buffer->available - 1 - buffer->used;
+}
+
+bool is_symbol(char c)
+{
+  return isalpha(c) || c == '-' || c == '_';
+}
+
+token_t tokenise_symbol(buffer_t *buffer)
+{
+  token_t token = {.type = TOKEN_SYMBOL, .str_size = 0};
+  for (; token.str_size < space_left(buffer) &&
+         is_symbol(buffer->data[buffer->used + token.str_size]);
+       ++token.str_size)
+    continue;
+  token.str = calloc(token.str_size + 1, 1);
+  memcpy(token.str, buffer->data + buffer->used, token.str_size);
+  token.str[token.str_size] = '\0';
+  buffer->used += token.str_size;
+  return token;
+}
+
+void tokenise_literal(buffer_t *buffer, token_t *token)
+{
+  token->str_size = 0;
+  for (; token->str_size < space_left(buffer) &&
+         isdigit(buffer->data[buffer->used + token->str_size]);
+       ++token->str_size)
+    continue;
+  token->str = calloc(token->str_size + 1, 1);
+  memcpy(token->str, buffer->data + buffer->used, token->str_size);
+  token->str[token->str_size] = '\0';
+  buffer->used += token->str_size;
+}
+
+token_t tokenise_byte_literal(buffer_t *buffer)
+{
+  token_t token = {.type = TOKEN_BYTE_LITERAL};
+  tokenise_literal(buffer, &token);
+  return token;
+}
+
+token_t tokenise_hword_literal(buffer_t *buffer)
+{
+  token_t token = {.type = TOKEN_HWORD_LITERAL};
+  tokenise_literal(buffer, &token);
+  return token;
+}
+
+token_t tokenise_word_literal(buffer_t *buffer)
+{
+  token_t token = {.type = TOKEN_WORD_LITERAL};
+  tokenise_literal(buffer, &token);
+  return token;
+}
+
+token_t *tokenise_buffer(buffer_t *buffer, size_t *n_tokens)
+{
+  buffer_t tokens = {0};
+  darr_init(&tokens, sizeof(token_t));
+  while (space_left(buffer) != 0)
+  {
+    bool is_token = true;
+    token_t t     = {0};
+    char c        = buffer->data[buffer->used];
+    if (isspace(c) || c == '\0')
+    {
+      // Clean whitespace
+      for (; space_left(buffer) > 0 && (isspace(c) || c == '\0');
+           ++buffer->used, c = buffer->data[buffer->used])
+        continue;
+      is_token = false;
+    }
+    else if (space_left(buffer) > 1 && isdigit(buffer->data[buffer->used + 1]))
+    {
+      // Parsing literals
+
+      switch (c)
+      {
+      case 'b':
+        buffer->used++;
+        t = tokenise_byte_literal(buffer);
+        break;
+      case 'h':
+        buffer->used++;
+        t = tokenise_hword_literal(buffer);
+        break;
+      case 'w':
+        buffer->used++;
+        t = tokenise_word_literal(buffer);
+        break;
+      default:
+        // TODO: Lex Error (INVALID_LITERAL)
+        fprintf(stderr, "[LEX_ERROR]: Invalid literal `%c`\n", c);
+        exit(1);
+      }
+    }
+    else if (is_symbol(c))
+    {
+      t = tokenise_symbol(buffer);
+    }
+    if (is_token)
+      darr_append_bytes(&tokens, (byte *)&t, sizeof(t));
+  }
+  *n_tokens = tokens.used / sizeof(token_t);
+  return (token_t *)tokens.data;
+}
 
 int main(void)
 {
-  FILE *fp    = fopen("main.asm", "rb");
-  darr_t darr = darr_read_file(fp);
+  FILE *fp        = fopen("main.asm", "rb");
+  buffer_t buffer = darr_read_file(fp);
   fclose(fp);
-  darr.data[darr.available - 1] = '\0';
-  printf("%lu/%lu\n%s\n", darr.used, darr.available, darr.data);
-  free(darr.data);
+
+  size_t n        = 0;
+  token_t *tokens = tokenise_buffer(&buffer, &n);
+  printf("%lu bytes -> %lu tokens\n", buffer.used, n);
+  free(buffer.data);
+
+  for (size_t i = 0; i < n; ++i)
+    printf("%s(%.*s)\n", token_type_as_cstr(tokens[i].type),
+           (int)tokens[i].str_size, tokens[i].str);
+
+  // Free the tokens
+  for (size_t i = 0; i < n; ++i)
+    free(tokens[i].str);
+  free(tokens);
   return 0;
 }
-- 
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