From 915d62ceef54fc491efda040d9d43fbdf558b591 Mon Sep 17 00:00:00 2001
From: Josh Holtrop <jholtrop@gmail.com>
Date: Sun, 27 Nov 2016 17:24:59 -0500
Subject: [PATCH] add GapBuffer::insert()

---
 src/core/Encoding.h   |  5 ++++
 src/core/GapBuffer.cc | 62 +++++++++++++++++++++++++++++++++++++++++++
 src/core/GapBuffer.h  |  4 +++
 3 files changed, 71 insertions(+)

diff --git a/src/core/Encoding.h b/src/core/Encoding.h
index f85defc..617f302 100644
--- a/src/core/Encoding.h
+++ b/src/core/Encoding.h
@@ -13,6 +13,11 @@ public:
         CP_1252,
     };
 
+    enum
+    {
+        MAX_CODE_POINT_SIZE = 8,
+    };
+
     static Type detect_encoding(const uint8_t * buffer, size_t length);
     static uint8_t num_bytes_in_code_point(Type type, const uint8_t * encoded);
     static const uint8_t * beginning_of_code_point(Type type, const uint8_t * encoded);
diff --git a/src/core/GapBuffer.cc b/src/core/GapBuffer.cc
index fe13f52..7c55ed9 100644
--- a/src/core/GapBuffer.cc
+++ b/src/core/GapBuffer.cc
@@ -43,6 +43,68 @@ void GapBuffer::compact()
     }
 }
 
+/**
+ * Insert code_point into the gap buffer at position position.
+ *
+ * @param position Position in the gap buffer to insert the code point at.
+ *   Must be <= size.
+ * @param code_point The code point to insert.
+ */
+void GapBuffer::insert(size_t position, uint32_t code_point)
+{
+    if (position > m_size)
+        return;
+    check_grow();
+    move_gap(position);
+    size_t size = Encoding::encode(code_point, m_encoding, &m_buffer[m_gap_position]);
+    m_gap_position += size;
+    m_size += size;
+}
+
+/**
+ * Verify that there is enough free space in the gap, and if not, grow the gap
+ * and move data.
+ */
+void GapBuffer::check_grow()
+{
+    if (gap_size() < Encoding::MAX_CODE_POINT_SIZE)
+    {
+        /* We're out of space. Allocate more and move. */
+        size_t new_size = (m_buffer_size + (128u * 1024u)) & System::page_base_mask;
+        size_t new_num_pages = new_size >> System::page_size_log;
+        uint8_t * new_buffer = (uint8_t *)System::alloc_pages(new_num_pages);
+        memcpy(new_buffer, m_buffer, m_gap_position);
+        memcpy(&new_buffer[m_gap_position], &m_buffer[m_gap_position + gap_size()], m_size - m_gap_position);
+
+        /* Free the old buffer */
+        System::free_pages(m_buffer, m_buffer_size >> System::page_size_log);
+
+        m_buffer = new_buffer;
+        m_buffer_size = new_size;
+        m_gap_position = m_size;
+    }
+}
+
+/**
+ * Move the gap buffer gap position to the requested position.
+ *
+ * @param position New gap position. Must be <= m_size.
+ */
+void GapBuffer::move_gap(size_t position)
+{
+    if (position != m_gap_position)
+    {
+        if (position < m_gap_position)
+        {
+            memmove(&m_buffer[position + gap_size()], &m_buffer[position], m_gap_position - position);
+        }
+        else
+        {
+            memmove(&m_buffer[m_gap_position], &m_buffer[m_gap_position + gap_size()], position - m_gap_position);
+        }
+    }
+}
+
 
 void GapBuffer::Iterator::go_forward()
 {
diff --git a/src/core/GapBuffer.h b/src/core/GapBuffer.h
index 3e86bc5..0100b89 100644
--- a/src/core/GapBuffer.h
+++ b/src/core/GapBuffer.h
@@ -110,6 +110,7 @@ public:
     }
     size_t gap_size() const { return m_buffer_size - m_size; }
     void compact();
+    void insert(size_t position, uint32_t code_point);
 
 protected:
     uint8_t * m_buffer;
@@ -118,6 +119,9 @@ protected:
     size_t m_gap_position;
     Encoding::Type m_encoding;
     std::list<std::shared_ptr<Cursor>> m_cursors;
+
+    void check_grow();
+    void move_gap(size_t position);
 };
 
 #endif