4 files changed, 77 insertions(+), 0 deletions(-)

A fs/doc/lib/endian.txt
A fs/lib/endian.fs
M fs/tests/lib/all.fs
A fs/tests/lib/endian.fs

@@ 0,0 1,26 @@
+# Endian-ness management
+
+This unit provides words to read and write numbers in an endian-ness that isn't
+the native one (or simply alias to the native ones if it is).
+
+At the moment, two endian-ness are supported, little-endian (LE) and big endian
+(BE). Let's consider this memory arrangement:
+
+A+0  A+1  A+2  A+3
+$12  $34  $56  $78
+
+When this memory is read as little endian, that is, the least significant byte
+first, it reads as $78563412. When it's read as big endian, that is, the most
+significant byte first, it reads as $12345678.
+
+Words provided:
+
+le@  a -- n   Little-endian fetch
+le!  n a --   Little-endian store
+be@  a -- n   Big-endian fetch
+be!  n a --   Big-endian store
+
+Each of these words have a 16-bit variant, so they can be called with a "16b"
+modulator. They don't have a "8b" one because it makes no sense.
+
+These words are implemented in HAL, so they're fast.

@@ 0,0 1,32 @@
+\ Endian-ness convenience words
+?f<< /asm/hal.fs
+
+$1234 here ! here c@ $34 = const LITTLE_ENDIAN?
+
+alias @ le@ :16b 16b @ ;
+alias ! le! :16b 16b ! ;
+LITTLE_ENDIAN? not [if] abort" TODO" [then]
+
+alias @ be@ :16b 16b @ ;
+alias ! be! :16b 16b ! ;
+LITTLE_ENDIAN? [if]
+  code be@ ( a -- n )
+    W>A, A) 8b) @, 8 i) <<,
+    A) 1 +) 8b) |, 8 i) <<,
+    A) 2 +) 8b) |, 8 i) <<,
+    A) 3 +) 8b) |, exit,
+
+  code16b
+    W>A, A) 8b) @, 8 i) <<,
+    A) 1 +) 8b) |, exit,
+
+  code be! ( n a -- )
+    W>A, drop, A) 3 +) 8b) !, 8 i) >>,
+    A) 2 +) 8b) !, 8 i) >>,
+    A) 1 +) 8b) !, 8 i) >>,
+    A) 8b) !, drop, exit,
+
+  code16b
+    W>A, drop, A) 1 +) 8b) !, 8 i) >>,
+    A) 8b) !, drop, exit,
+[then]<
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@@ 15,3 15,4 @@ f<< /tests/lib/stack.fs
 f<< /tests/lib/tree.fs
 f<< /tests/lib/fmt.fs
 f<< /tests/lib/crc.fs
+f<< /tests/lib/endian.fs

@@ 0,0 1,18 @@
+?f<< /tests/harness.fs
+?f<< /lib/endian.fs
+testbegin
+\ Endian-ness tests
+create mynum 4 nc, $12 $34 $56 $78
+mynum le@ $78563412 #eq
+mynum 16b le@ $3412 #eq
+mynum be@ $12345678 #eq
+mynum 16b be@ $1234 #eq
+$23456789 mynum le!
+mynum be@ $89674523 #eq
+0 mynum ! $2345 mynum 16b le!
+mynum be@ $45230000 #eq
+$23456789 mynum be!
+mynum le@ $89674523 #eq
+0 mynum ! $2345 mynum 16b be!
+mynum le@ $4523 #eq
+testend<
\ No newline at end of file