From 54bb3c9abdd34b92be44b87382a7b3c03a5991d9 Mon Sep 17 00:00:00 2001
From: Ian C <ianc@noddybox.co.uk>
Date: Fri, 2 Sep 2016 08:19:29 +0000
Subject: Added README and clamped code point values.

---
 README      | 53 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 ascii2map.c | 24 +++++++++++++++++++++---
 example     |  3 ++-
 3 files changed, 76 insertions(+), 4 deletions(-)
 create mode 100644 README

diff --git a/README b/README
new file mode 100644
index 0000000..e01202a
--- /dev/null
+++ b/README
@@ -0,0 +1,53 @@
+USAGE
+=====
+This is a simple tool to generate data for a map as defined using ASCII art.
+
+usage: ascii2map [-a|-b|-c] [-d directive] [input-file [output-file]]
+
+SWITCHES
+========
+
+-a		The default.  Produce assembly output.
+-b		Produce binary output.
+-c		Produce C source output.
+-d "x"		In assembly mode use "x" as the directive instead of the
+		default "byte".
+input-file	The input file.  If not supplied stdin is used.
+output-file	The output file.  If not supplied stdout is used.
+
+
+INPUT FILES
+===========
+
+Input files look like the following:
+
+#:1
+*:128
+!63
+~
+########
+#      #
+#ABCDEF#
+#1# # *#
+########
+
+The "#:1" line defines that when a '#' character appears in the map then code
+'1' should be used.
+
+The following line defines the offset for any characters that aren't explicitly
+defined.  e.g. in this example 63 will be deducted from the character code.
+In ASCII this would mean 'A' becomes 2, 'B' becomes 3, and so on.  Any codes
+generated that fall outside the range 0 to 255 will be clamped to that range.
+
+The line with a tilde (~) on its own indicates the end of the definitions.
+
+Following it is the map to produce the definition for, eg.
+
+$ ascii2map example
+	byte	1, 1, 1, 1, 1, 1, 1, 1
+	byte	1, 0, 0, 0, 0, 0, 0, 1
+	byte	1, 2, 3, 4, 5, 6, 7, 1
+	byte	1, 0, 1, 0, 1, 0, 128, 1
+	byte	1, 1, 1, 1, 1, 1, 1, 1
+
+The following switch
diff --git a/ascii2map.c b/ascii2map.c
index 30a2c44..f24cb77 100644
--- a/ascii2map.c
+++ b/ascii2map.c
@@ -105,6 +105,24 @@ static void EndOutput(FILE *fp)
 }
 
 
+static unsigned CodePoint(char c)
+{
+    int offset = c - code_point;
+
+    if (offset < 0)
+    {
+        offset = 0;
+    }
+
+    if (offset > 255)
+    {
+        offset = 255;
+    }
+
+    return (unsigned)offset;
+}
+
+
 static void Output(FILE *fp, char c)
 {
     static int column;
@@ -138,7 +156,7 @@ static void Output(FILE *fp, char c)
             }
             else
             {
-                fprintf(fp, "%u", c - code_point);
+                fprintf(fp, "%u", CodePoint(c));
             }
 
             break;
@@ -150,7 +168,7 @@ static void Output(FILE *fp, char c)
             }
             else
             {
-                putc(c - code_point, fp);
+                putc(CodePoint(c), fp);
             }
 
             break;
@@ -177,7 +195,7 @@ static void Output(FILE *fp, char c)
             }
             else
             {
-                fprintf(fp, "%u", c - code_point);
+                fprintf(fp, "%u", CodePoint(c));
             }
 
             break;
diff --git a/example b/example
index e89d67d..329c0b6 100644
--- a/example
+++ b/example
@@ -1,8 +1,9 @@
 #:1
+*:128
 !63
 ~
 ########
 #      #
 #ABCDEF#
-# # # ##
+#1# # *#
 ########
-- 
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