From: Michael D. Lowis <mike.lowis@gentex.com>
Date: Tue, 4 Jan 2022 21:31:14 +0000 (-0500)
Subject: pulled in UTF8 encoder/decoder and updated TODO list
X-Git-Url: https://git.mdlowis.com/?a=commitdiff_plain;h=b4c8dde0fd929c86782b6862e522455b6bf7f711;p=proto%2Faos.git

pulled in UTF8 encoder/decoder and updated TODO list
---

diff --git a/TODO.md b/TODO.md
index e9340da..5be09ac 100644
--- a/TODO.md
+++ b/TODO.md
@@ -1,20 +1,17 @@
 # Doing
 
-* Finish option parsing logic (remove mallocs, handle positional args)
+* Add JSON parser/generator (binary and text)
+    * [UBJSON](https://en.wikipedia.org/wiki/UBJSON)
+    * [JSMN](https://github.com/zserge/jsmn)
 
 # On Deck
 
-* Add support for complex binary targets
+* Add ubus-like IPC daemon
 * Add tide-like text editor
 
 # Backlog
 
-* Add JSON parser/generator (binary and text)
-    * [UBJSON](https://en.wikipedia.org/wiki/UBJSON)
-    * [JSMN](https://github.com/zserge/jsmn)
-* Add ubus-like IPC daemon
+* Add INI (or TOML) parser to liba
 * Add Icon-like language interpreter
-* Combine libnet and liba
 * Add MDL markup language processor
-* Add INI (or TOML) parser to liba
 * Add ANSI terminal support to liba
diff --git a/inc/liba.h b/inc/liba.h
index b8e4e73..6e5a038 100644
--- a/inc/liba.h
+++ b/inc/liba.h
@@ -76,6 +76,20 @@ int Net_Accept(int fd);
 int Net_Dial(char* dialstr);
 void Net_Serve(char* dialstr, void (*on_client)(int cfd));
 
+/*
+    UTF8 Encoding and Decoding
+*/
+#define UTF_MAX   6u
+#define RUNE_SELF ((Rune)0x80)
+#define RUNE_ERR  ((Rune)0xFFFD)
+#define RUNE_MAX  ((Rune)0x10FFFF)
+#define RUNE_EOF  ((Rune)EOF)
+
+typedef uint32_t Rune;
+
+size_t UTF8_Encode(char str[UTF_MAX], Rune rune);
+bool UTF8_Decode(Rune* rune, size_t* length, int byte);
+
 /*
     Basic Runtime Facilities
 */
diff --git a/lib/a/UTF8.c b/lib/a/UTF8.c
new file mode 100644
index 0000000..5a39bb8
--- /dev/null
+++ b/lib/a/UTF8.c
@@ -0,0 +1,84 @@
+#include <liba.h>
+
+static const uint8_t UTF8_SeqBits[] = { 0x00u, 0x80u, 0xC0u, 0xE0u, 0xF0u, 0xF8u, 0xFCu, 0xFEu };
+static const uint8_t UTF8_SeqMask[] = { 0x00u, 0xFFu, 0x1Fu, 0x0Fu, 0x07u, 0x03u, 0x01u, 0x00u };
+static const uint8_t UTF8_SeqLens[] = { 0x01u, 0x00u, 0x02u, 0x03u, 0x04u, 0x05u, 0x06u, 0x00u };
+
+static bool runevalid(Rune val) {
+    return (val <= RUNE_MAX)
+        && ((val & 0xFFFEu) != 0xFFFEu)
+        && ((val < 0xD800u) || (val > 0xDFFFu))
+        && ((val < 0xFDD0u) || (val > 0xFDEFu));
+}
+
+static size_t runelen(Rune rune) {
+    if(!runevalid(rune))
+        return 0;
+    else if(rune <= 0x7F)
+        return 1;
+    else if(rune <= 0x07FF)
+        return 2;
+    else if(rune <= 0xFFFF)
+        return 3;
+    else
+        return 4;
+}
+
+static uint8_t utfseq(uint8_t byte) {
+    for (int i = 1; i < 8; i++)
+        if ((byte & UTF8_SeqBits[i]) == UTF8_SeqBits[i-1])
+            return UTF8_SeqLens[i-1];
+    return 0;
+}
+
+size_t UTF8_Encode(char str[UTF_MAX], Rune rune)
+{
+    size_t len = runelen(rune);
+    str[0] = (len == 1 ? 0x00 : UTF8_SeqBits[len])
+           | (UTF8_SeqMask[len] & (rune >> (6 * (len-1))));
+    for (size_t i = 1; i < len; i++)
+    {
+        str[i] = 0x80u | (0x3Fu & (rune >> (6 * (len-i-1))));
+    }
+    return len;
+}
+
+bool UTF8_Decode(Rune* rune, size_t* length, int byte)
+{
+    /* Handle the start of a new rune */
+    if (*length == 0)
+    {
+        /* If we were fed in an EOF as a start byte, handle it here */
+        if (byte == EOF)
+        {
+            *rune = RUNE_EOF;
+        }
+        else
+        {
+            /* Otherwise, decode the first byte of the rune */
+            *length = utfseq(byte);
+            *rune   = (*length == 0) ? RUNE_ERR : (byte & UTF8_SeqMask[*length]);
+            (*length)--;
+        }
+    }
+    /* Handle continuation bytes */
+    else if ((byte & 0xC0) == 0x80)
+    {
+        /* add bits from continuation byte to rune value
+         * cannot overflow: 6 byte sequences contain 31 bits */
+        *rune = (*rune << 6) | (byte & 0x3F); /* 10xxxxxx */
+        (*length)--;
+        /* Sanity check the final rune value before finishing */
+        if ((*length == 0) && !runevalid(*rune))
+        {
+            *rune = RUNE_ERR;
+        }
+    }
+    /* Didn't get the continuation byte we expected */
+    else
+    {
+        *rune = RUNE_ERR;
+    }
+    /* Tell the caller whether we finished or not */
+    return ((*length == 0) || (*rune == RUNE_ERR));
+}