From c660341f900d5ca9944248b6a8c6599341b77a6f Mon Sep 17 00:00:00 2001
From: offtkp <parisoplop@gmail.com>
Date: Fri, 1 Nov 2024 19:22:16 +0200
Subject: [PATCH] assembler: Allow cursor to be moved forwards

---
 include/biscuit/assembler.hpp   | 12 ++++++++++++
 include/biscuit/code_buffer.hpp | 24 ++++++++++++++++++++----
 2 files changed, 32 insertions(+), 4 deletions(-)

diff --git a/include/biscuit/assembler.hpp b/include/biscuit/assembler.hpp
index 30db402..069656a 100644
--- a/include/biscuit/assembler.hpp
+++ b/include/biscuit/assembler.hpp
@@ -112,6 +112,18 @@ class Assembler {
         m_buffer.RewindCursor(offset);
     }
 
+    /**
+     * Allows advancing of the code buffer cursor.
+     * 
+     * @param offset The offset to advance the cursor by.
+     *
+     * @note The offset may not be smaller than the current cursor offset 
+     *       and may not be larger than the current buffer capacity.
+     */
+    void AdvanceBuffer(ptrdiff_t offset) {
+        m_buffer.AdvanceCursor(offset);
+    }
+
     /// Retrieves the cursor pointer for the underlying code buffer.
     [[nodiscard]] uint8_t* GetCursorPointer() noexcept {
         return m_buffer.GetCursorPointer();
diff --git a/include/biscuit/code_buffer.hpp b/include/biscuit/code_buffer.hpp
index 46314e4..9998236 100644
--- a/include/biscuit/code_buffer.hpp
+++ b/include/biscuit/code_buffer.hpp
@@ -88,14 +88,16 @@ class CodeBuffer {
 
     /// Retrieves the pointer to an arbitrary location within the buffer.
     [[nodiscard]] uint8_t* GetOffsetPointer(ptrdiff_t offset) noexcept {
-        BISCUIT_ASSERT(offset >= 0 && offset <= GetCursorOffset());
-        return m_buffer + offset;
+        auto pointer = m_buffer + offset;
+        BISCUIT_ASSERT(pointer >= m_buffer && pointer < m_buffer + m_capacity);
+        return pointer;
     }
 
     /// Retrieves the pointer to an arbitrary location within the buffer.
     [[nodiscard]] const uint8_t* GetOffsetPointer(ptrdiff_t offset) const noexcept {
-        BISCUIT_ASSERT(offset >= 0 && offset <= GetCursorOffset());
-        return m_buffer + offset;
+        auto pointer = m_buffer + offset;
+        BISCUIT_ASSERT(pointer >= m_buffer && pointer < m_buffer + m_capacity);
+        return pointer;
     }
 
     /**
@@ -115,6 +117,20 @@ class CodeBuffer {
         m_cursor = rewound;
     }
 
+    /**
+     * Allows advancing of the code buffer cursor.
+     * 
+     * @param offset The offset to advance the cursor by.
+     *
+     * @note The offset may not be smaller than the current cursor offset 
+     *       and may not be larger than the current buffer capacity.
+     */
+    void AdvanceCursor(ptrdiff_t offset) noexcept {
+        auto* forward = m_buffer + offset;
+        BISCUIT_ASSERT(m_cursor <= forward && forward < m_buffer + m_capacity);
+        m_cursor = forward;
+    }
+
     /**
      * Whether or not the underlying buffer has enough room for the
      * given number of bytes.