Squashed 'src/univalue/' content from commit 9ef5b78

git-subtree-dir: src/univalue
git-subtree-split: 9ef5b78c1998509b8f1ccd76f0aee15140e384be

lib/univalue_utffilter.h

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+// Copyright 2016 Wladimir J. van der Laan
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+#ifndef UNIVALUE_UTFFILTER_H
+#define UNIVALUE_UTFFILTER_H
+
+#include <string>
+
+/**
+ * Filter that generates and validates UTF-8, as well as collates UTF-16
+ * surrogate pairs as specified in RFC4627.
+ */
+class JSONUTF8StringFilter
+{
+public:
+    JSONUTF8StringFilter(std::string &s):
+        str(s), is_valid(true), codepoint(0), state(0), surpair(0)
+    {
+    }
+    // Write single 8-bit char (may be part of UTF-8 sequence)
+    void push_back(unsigned char ch)
+    {
+        if (state == 0) {
+            if (ch < 0x80) // 7-bit ASCII, fast direct pass-through
+                str.push_back(ch);
+            else if (ch < 0xc0) // Mid-sequence character, invalid in this state
+                is_valid = false;
+            else if (ch < 0xe0) { // Start of 2-byte sequence
+                codepoint = (ch & 0x1f) << 6;
+                state = 6;
+            } else if (ch < 0xf0) { // Start of 3-byte sequence
+                codepoint = (ch & 0x0f) << 12;
+                state = 12;
+            } else if (ch < 0xf8) { // Start of 4-byte sequence
+                codepoint = (ch & 0x07) << 18;
+                state = 18;
+            } else // Reserved, invalid
+                is_valid = false;
+        } else {
+            if ((ch & 0xc0) != 0x80) // Not a continuation, invalid
+                is_valid = false;
+            state -= 6;
+            codepoint |= (ch & 0x3f) << state;
+            if (state == 0)
+                push_back_u(codepoint);
+        }
+    }
+    // Write codepoint directly, possibly collating surrogate pairs
+    void push_back_u(unsigned int codepoint_)
+    {
+        if (state) // Only accept full codepoints in open state
+            is_valid = false;
+        if (codepoint_ >= 0xD800 && codepoint_ < 0xDC00) { // First half of surrogate pair
+            if (surpair) // Two subsequent surrogate pair openers - fail
+                is_valid = false;
+            else
+                surpair = codepoint_;
+        } else if (codepoint_ >= 0xDC00 && codepoint_ < 0xE000) { // Second half of surrogate pair
+            if (surpair) { // Open surrogate pair, expect second half
+                // Compute code point from UTF-16 surrogate pair
+                append_codepoint(0x10000 | ((surpair - 0xD800)<<10) | (codepoint_ - 0xDC00));
+                surpair = 0;
+            } else // Second half doesn't follow a first half - fail
+                is_valid = false;
+        } else {
+            if (surpair) // First half of surrogate pair not followed by second - fail
+                is_valid = false;
+            else
+                append_codepoint(codepoint_);
+        }
+    }
+    // Check that we're in a state where the string can be ended
+    // No open sequences, no open surrogate pairs, etc
+    bool finalize()
+    {
+        if (state || surpair)
+            is_valid = false;
+        return is_valid;
+    }
+private:
+    std::string &str;
+    bool is_valid;
+    // Current UTF-8 decoding state
+    unsigned int codepoint;
+    int state; // Top bit to be filled in for next UTF-8 byte, or 0
+
+    // Keep track of the following state to handle the following section of
+    // RFC4627:
+    //
+    //    To escape an extended character that is not in the Basic Multilingual
+    //    Plane, the character is represented as a twelve-character sequence,
+    //    encoding the UTF-16 surrogate pair.  So, for example, a string
+    //    containing only the G clef character (U+1D11E) may be represented as
+    //    "\uD834\uDD1E".
+    //
+    //  Two subsequent \u.... may have to be replaced with one actual codepoint.
+    unsigned int surpair; // First half of open UTF-16 surrogate pair, or 0
+
+    void append_codepoint(unsigned int codepoint_)
+    {
+        if (codepoint_ <= 0x7f)
+            str.push_back((char)codepoint_);
+        else if (codepoint_ <= 0x7FF) {
+            str.push_back((char)(0xC0 | (codepoint_ >> 6)));
+            str.push_back((char)(0x80 | (codepoint_ & 0x3F)));
+        } else if (codepoint_ <= 0xFFFF) {
+            str.push_back((char)(0xE0 | (codepoint_ >> 12)));
+            str.push_back((char)(0x80 | ((codepoint_ >> 6) & 0x3F)));
+            str.push_back((char)(0x80 | (codepoint_ & 0x3F)));
+        } else if (codepoint_ <= 0x1FFFFF) {
+            str.push_back((char)(0xF0 | (codepoint_ >> 18)));
+            str.push_back((char)(0x80 | ((codepoint_ >> 12) & 0x3F)));
+            str.push_back((char)(0x80 | ((codepoint_ >> 6) & 0x3F)));
+            str.push_back((char)(0x80 | (codepoint_ & 0x3F)));
+        }
+    }
+};
+
+#endif