From cd5dec55b206b8348efa34741ab74a8859ef938e Mon Sep 17 00:00:00 2001
From: Jamie Reece Wilson <me@reece.sx>
Date: Fri, 14 Jun 2024 14:14:51 +0100
Subject: [PATCH] [+] Util: AuCodepointsForEach

---
 Include/auROXTL/auStringUtils.hpp | 85 ++++++++++++++++++++++++++++++-
 1 file changed, 83 insertions(+), 2 deletions(-)

diff --git a/Include/auROXTL/auStringUtils.hpp b/Include/auROXTL/auStringUtils.hpp
index ec9689b..7b86513 100644
--- a/Include/auROXTL/auStringUtils.hpp
+++ b/Include/auROXTL/auStringUtils.hpp
@@ -30,6 +30,12 @@
 // offset in codepoints
 /* using CodepointOffset_t = AuUInt; */
 
+#if defined(AURORA_I_SUCK_AND_WANT_MODERN_UTF8)
+    static const AuUInt8 kAuCodepointUTF8MaxBytes = 4;
+#else
+    static const AuUInt8 kAuCodepointUTF8MaxBytes = 6;
+#endif
+
 static auline constexpr bool AuStringContains(const AuROString &value, const AuROString &subpattern)
 {
     return value.find(subpattern) != AuROString::npos;
@@ -296,7 +302,7 @@ static AuList<AuUInt32> AuCodepointsDecode(const AuROString &in)
             {
             }
 
-            if (nby > 6)
+            if (nby > kAuCodepointUTF8MaxBytes)
             {
                 return {};
             }
@@ -420,7 +426,7 @@ static AuString AuCodepointsTransform(T op, const AuROString &in)
             {
             }
 
-            if (nby > 6)
+            if (nby > kAuCodepointUTF8MaxBytes)
             {
                 return {};
             }
@@ -453,6 +459,81 @@ static AuString AuCodepointsTransform(T op, const AuROString &in)
     return ret;
 }
 
+template <class T>
+static bool AuCodepointsForEach(T op, const AuROString &in)
+{
+    if (in.empty())
+    {
+        return true;
+    }
+
+    auto uLength = in.length();
+
+    const char *pItr = in.data();
+    const char *pEnd = pItr + uLength;
+
+    while (pItr < pEnd)
+    {
+        AuUInt32 c {};
+
+        if ((c = *pItr) <= 0x7FU)
+        {
+            ++pItr;
+        }
+        else
+        {
+            AuUInt32 nby {};
+
+            if ((*pItr & 0xC0U) != 0xC0U)
+            {
+                return false;
+            }
+
+            for (AuUInt8 b = *pItr; (b & 0x80U) != 0; b <<= 1, ++nby)
+            {
+            }
+
+            if (nby > kAuCodepointUTF8MaxBytes)
+            {
+                return false;
+            }
+
+            if (AuUInt(pEnd - pItr) < AuUInt(nby))
+            {
+                return false;
+            }
+
+            c = *pItr & (AuUInt8(0xFFU) >> (nby + 1));
+
+            for (AuUInt32 i = 1; i < nby; ++i)
+            {
+                if ((pItr[i] & 0xC0U) != 0x80U)
+                {
+                    return {};
+                }
+
+                c = (c << 6) | (pItr[i] & 0x3FU);
+            }
+
+            pItr += nby;
+        }
+
+        if constexpr (AuIsSame_v<AuResultOf_t<T, AuUInt32>, bool>)
+        {
+            if (!op(c))
+            {
+                return false;
+            }
+        }
+        else
+        {
+            op(c);
+        }
+    }
+
+    return true;
+}
+
 static auline CodepointByteOffset_t AuCodepointsGetByteOffset(const AuROString &in,
                                                               CodepointOffset_t uCodepointIndex)
 {