From 9f0dc52934d3ee4e8fe7eddd9abb19380a0e39c8 Mon Sep 17 00:00:00 2001
From: Jesse McDonald <nybble41@gmail.com>
Date: Sat, 14 Nov 2009 17:35:34 -0600
Subject: [PATCH] Improve number-reading in preparation for supporting
 floating-point.

---
 reader.c | 87 ++++++++++++++++++++++++++++++++++++++++----------------
 1 file changed, 62 insertions(+), 25 deletions(-)

diff --git a/reader.c b/reader.c
index 50f4e81..0260aaa 100644
--- a/reader.c
+++ b/reader.c
@@ -21,6 +21,7 @@ typedef struct reader_state
 static value_t read_one_value(reader_state_t *state);
 static value_t read_special(reader_state_t *state);
 static value_t read_list(reader_state_t *state);
+static value_t read_fixnum(reader_state_t *state, int radix);
 static value_t read_number(reader_state_t *state);
 static value_t read_string(reader_state_t *state);
 
@@ -79,6 +80,7 @@ static value_t read_one_value(reader_state_t *state)
   case '(':
     return read_list(state);
   case '-':
+  case '+':
   case '0' ... '9':
     return read_number(state);
   case '\"':
@@ -215,12 +217,26 @@ static value_t read_list(reader_state_t *state)
   return list_root.value;
 }
 
-static value_t read_number(reader_state_t *state)
+static short int char_to_digit(int ch)
+{
+  if (isdigit(ch))
+  {
+    return ch - '0';
+  }
+  else
+  {
+    assert(isalpha(ch));
+    return 10 + (toupper(ch) - 'A');
+  }
+}
+
+static value_t read_fixnum(reader_state_t *state, int radix)
 {
-  fixnum_t radix = 10;
   fixnum_t num = 0;
   bool negative = false;
 
+  assert((0 <= radix) && (radix <= 36));
+
   if (state->ch == '-')
   {
     negative = true;
@@ -233,35 +249,49 @@ static value_t read_number(reader_state_t *state)
 
   release_assert(isdigit(state->ch));
 
-  if (state->ch == '0')
+  if (radix == 0)
   {
-    next_char(state);
-
-    switch (state->ch)
+    if (state->ch == '0')
     {
-    case 'X':
-    case 'x':
       next_char(state);
-      radix = 16;
-      break;
-    case 'B':
-    case 'b':
-      next_char(state);
-      radix = 2;
-      break;
-    default:
-      radix = 8;
-      break;
+
+      switch (state->ch)
+      {
+      case 'X':
+      case 'x':
+        next_char(state);
+        radix = 16;
+        break;
+      case 'B':
+      case 'b':
+        next_char(state);
+        radix = 2;
+        break;
+      default:
+        radix = 8;
+        break;
+      }
+
+      if (radix != 8)
+      {
+        /* Make sure we have at least one digit; if octal then the '0' counts instead */
+        release_assert(isalnum(state->ch));
+        release_assert(char_to_digit(state->ch) < radix);
+      }
+    }
+    else
+    {
+      radix = 10;
     }
   }
 
-  while (isxdigit(state->ch))
+  while (isalnum(state->ch))
   {
-    fixnum_t digit = isdigit(state->ch)
-                       ? (state->ch - '0')
-                       : (10 + (toupper(state->ch) - 'A'));
+    fixnum_t digit = char_to_digit(state->ch);
+
+    if (digit >= radix)
+      break;
 
-    release_assert(digit < radix);
     release_assert(num <= (FIXNUM_MAX/radix));
 
     num *= radix;
@@ -277,6 +307,13 @@ static value_t read_number(reader_state_t *state)
   return fixnum_value(num);
 }
 
+static value_t read_number(reader_state_t *state)
+{
+  value_t v = read_fixnum(state, 0);
+  release_assert(!issymbol(state->ch));
+  return v;
+}
+
 static value_t read_string(reader_state_t *state)
 {
   char *buffer = (char*)malloc(128);
@@ -484,7 +521,7 @@ static value_t read_weak_box(reader_state_t *state)
 
 static value_t read_definition(reader_state_t *state)
 {
-  fixnum_t ref = get_fixnum(read_number(state));
+  fixnum_t ref = get_fixnum(read_fixnum(state, 0));
   gc_root_t place_root;
   value_t v;
 
@@ -514,7 +551,7 @@ static value_t read_placeholder(reader_state_t *state)
   }
   else
   {
-    return get_placeholder(state, get_fixnum(read_number(state)));
+    return get_placeholder(state, get_fixnum(read_fixnum(state, 0)));
   }
 }