From 2a0dc1f064a364d8777085f396ce102679445796 Mon Sep 17 00:00:00 2001
From: Jamie Reece Wilson <me@reece.sx>
Date: Fri, 19 Apr 2024 23:12:39 +0100
Subject: [PATCH] [+] AuCodepointsFindPreviousValidByteOffsetFromOffset [+]
 AuCodepointsFindPreviousValidByteOffsetFromByteOffset [+]
 AuCodepointsFindCodepointOffset

---
 Include/auROXTL/auStringUtils.hpp | 125 +++++++++++++++++++++++++++++-
 1 file changed, 121 insertions(+), 4 deletions(-)

diff --git a/Include/auROXTL/auStringUtils.hpp b/Include/auROXTL/auStringUtils.hpp
index 388f6f5..f3dd997 100644
--- a/Include/auROXTL/auStringUtils.hpp
+++ b/Include/auROXTL/auStringUtils.hpp
@@ -15,9 +15,10 @@
     Implements: AuCodepointsTransform, AuCodepointsTransformASCIIOp, AuCodepointsToLower, AuCodepointsToUpper,
                 AuCodepointsCount, AuCodepointsNextLength, AuCodepointsDecode, AuCodepointsEncodeInto,
                 AuCodepointsGetByteOffset(CodepointOffset_t),AuCodepointsGetByteLength(CodepointOffset_t),
-                AuCodepointsFindByteOffset[Unsafe], AuCodepointsFindCodepointOffset,
+                AuCodepointsFindByteOffset[Unsafe], AuCodepointsFindCodepointOffset(view, CodepointOffset_t), AuCodepointsFindCodepointOffset(CodepointByteOffset_t),
                 AuCodepointsContains,
-                AuCodepointsReplaceAll, AuCodepointsSplitString (views)
+                AuCodepointsReplaceAll, AuCodepointsSplitString (views),
+                AuCodepointsFindPreviousValidByteOffsetFromOffset, AuCodepointsFindPreviousValidByteOffsetFromByteOffset
 
     For translating between locales (including utf8-32), defer to AuLocale (Aurora::Locale) in the Aurora Runtime.
 ***/
@@ -591,7 +592,7 @@ static CodepointByteOffset_t AuCodepointsFindByteOffset(const AuROString &in,
                                                         const AuROString &find,
                                                         CodepointByteOffset_t uStartPosition = {})
 {      
-    AuUInt uCounter {};
+    AuUInt uCounter    = 0;
     auto uLength       = in.length();
     auto uFindLength   = find.length();
 
@@ -670,7 +671,7 @@ static CodepointByteOffset_t AuCodepointsFindByteOffsetUnsafe(const AuROString &
                                                               const AuROString &find,
                                                               CodepointByteOffset_t uStartPosition = {})
 {      
-    AuUInt uCounter {};
+    AuUInt uCounter    = 0;
     auto uLength       = in.length();
     auto uFindLength   = find.length();
 
@@ -744,6 +745,122 @@ static CodepointByteOffset_t AuCodepointsFindByteOffsetUnsafe(const AuROString &
     return AuROString::npos;
 }
 
+static CodepointByteOffset_t AuCodepointsFindPreviousValidByteOffsetFromOffset(const AuROString &in,
+                                                                               CodepointOffset_t uStartPosition = {})
+{      
+    AuUInt uCounter    = 0;
+    auto uLength       = in.length();
+
+    const char *pStart = in.data();
+    const char *pItr   = pStart;
+    const char *pEnd   = pStart + uLength;
+
+    if (uStartPosition == 0)
+    {
+        return AuROString::npos;
+    }
+
+    while (pItr != pEnd)
+    {
+        AuUInt32     nby {};
+        auto         ch = *pItr;
+        unsigned int result = (ch & 0xF0);
+
+        if ((ch & 0x80) == 0)
+        {
+            nby = 1;
+        }
+        else if ((ch & 0xE0) == 0xC0)
+        {
+            nby = 2;
+        }
+        else if (result == 0xE0)
+        {
+            nby = 3;
+        }
+        else if (result == 0xF0)
+        {
+            if ((ch & 0x08) == 0x08)
+            {
+                // Special/Historic UTF8
+                nby = 5;
+            }
+            else if ((ch & 0x0c) == 0x0c)
+            {
+                // Special/Historic UTF8
+                nby = 6;
+            }
+            else
+            {
+                nby = 4;
+            }
+        }
+        else
+        {
+            break;
+        }
+
+        if (pItr + nby > pEnd)
+        {
+            break;
+        }
+
+        uCounter++;
+
+        if (uCounter == uStartPosition)
+        {
+            return CodepointByteOffset_t(pItr - pStart);
+        }
+
+        pItr += nby;
+    }
+
+    return AuROString::npos;
+}
+
+static CodepointByteOffset_t AuCodepointsFindPreviousValidByteOffsetFromByteOffset(const AuROString &in,
+                                                                                   CodepointByteOffset_t uStartPosition = {})
+{      
+    const char * pStart = in.data();
+    const char * pItr   = pStart + uStartPosition - 1;
+
+    if (uStartPosition == 0)
+    {
+        return AuROString::npos;
+    }
+    else if ((*pItr & 0x80) == 0)
+    {
+        return uStartPosition - 1;
+    }
+    else
+    {
+        while (pItr != pStart)
+        {
+            if ((*pItr & 0xC0U) == 0x80U)
+            {
+                pItr--;
+            }
+            else
+            {
+                break;
+            }
+        }
+
+        if ((*pItr & 0xC0U) != 0xC0U)
+        {
+            return AuROString::npos;
+        }
+
+        return CodepointByteOffset_t(pItr - pStart);
+    }
+}
+
+static CodepointOffset_t AuCodepointsFindCodepointOffset(const AuROString &in,
+                                                         CodepointByteOffset_t uBytePosition)
+{
+    return AuCodepointsCount(in.substr(0, uBytePosition));
+}
+
 static CodepointOffset_t AuCodepointsFindCodepointOffset(const AuROString &in,
                                                          const AuROString &find,
                                                          CodepointOffset_t uStartPosition = {})