From 54dcc516279d6d57b0bb41b52bd661ee641e07c7 Mon Sep 17 00:00:00 2001
From: Oliver Maskery <omaskery@googlemail.com>
Date: Fri, 30 May 2025 16:24:55 +0100
Subject: [PATCH] Expose max_freq option

---
 src/lzss_huff.rs           | 11 +++++++----
 src/td0.rs                 |  3 ++-
 src/tools/adaptive_huff.rs | 12 ++++++------
 3 files changed, 15 insertions(+), 11 deletions(-)

diff --git a/src/lzss_huff.rs b/src/lzss_huff.rs
index 27a8bc7..eed5085 100644
--- a/src/lzss_huff.rs
+++ b/src/lzss_huff.rs
@@ -36,7 +36,9 @@ pub struct Options {
     /// backfill symbol for LZSS dictionary
     pub precursor: u8,
     /// return error if file is larger
-    pub max_file_size: u64
+    pub max_file_size: u64,
+    /// updates tree when the root frequency comes to this value.
+    pub max_freq: usize,
 }
 
 pub const STD_OPTIONS: Options = Options {
@@ -47,7 +49,8 @@ pub const STD_OPTIONS: Options = Options {
     threshold: 2,
     lookahead: 60,
     precursor: b' ',
-    max_file_size: u32::MAX as u64/4
+    max_file_size: u32::MAX as u64/4,
+    max_freq: 0x8000,
 };
 
 /// Structure to perform the LZSS stage of  compression.
@@ -243,7 +246,7 @@ where R: Read + Seek, W: Write + Seek {
     // init
     let mut bytes = reader.bytes();
     let mut lzss = LZSS::create(opt.clone());
-    let mut huff = AdaptiveHuffmanCoder::create(256 + opt.lookahead - opt.threshold);
+    let mut huff = AdaptiveHuffmanCoder::create(opt.max_freq, 256 + opt.lookahead - opt.threshold);
     // setup dictionary
     let start_pos = opt.window_size - opt.lookahead;
     for i in 0..start_pos {
@@ -339,7 +342,7 @@ where R: Read + Seek, W: Write + Seek {
        false => u32::MAX
     };
     // init
-    let mut huff = AdaptiveHuffmanDecoder::create(256 + opt.lookahead - opt.threshold);
+    let mut huff = AdaptiveHuffmanDecoder::create(opt.max_freq, 256 + opt.lookahead - opt.threshold);
     let mut lzss= LZSS::create(opt.clone());
     let start_pos = opt.window_size - opt.lookahead;
 	for i in 0..start_pos {
diff --git a/src/td0.rs b/src/td0.rs
index 2a3c41e..e2b8103 100644
--- a/src/td0.rs
+++ b/src/td0.rs
@@ -55,7 +55,8 @@ pub const TD_V2_OPTIONS: lzss_huff::Options = lzss_huff::Options {
     threshold: 2,
     lookahead: 60,
     precursor: b' ',
-    max_file_size: 3_000_000
+    max_file_size: 3_000_000,
+    max_freq: 0x8000,
 };
 
 /// Convert a TD0 image from advanced compression to normal.
diff --git a/src/tools/adaptive_huff.rs b/src/tools/adaptive_huff.rs
index 2c73207..1c39ca2 100644
--- a/src/tools/adaptive_huff.rs
+++ b/src/tools/adaptive_huff.rs
@@ -139,9 +139,9 @@ const D_CODE: [u8;256] = [
 ];
 
 impl AdaptiveHuffmanTree {
-    pub fn create(num_symbols: usize) -> Self {
+    pub fn create(max_freq: usize, num_symbols: usize) -> Self {
         let mut ans = Self {
-            max_freq: 0x8000,
+            max_freq,
             num_symb: num_symbols,
             node_count: 2*num_symbols - 1,
             root: 2*num_symbols - 2,
@@ -292,9 +292,9 @@ impl AdaptiveHuffmanTree {
 }
 
 impl AdaptiveHuffmanCoder {
-    pub fn create(num_symbols: usize) -> Self {
+    pub fn create(max_freq: usize, num_symbols: usize) -> Self {
         Self {
-            tree: AdaptiveHuffmanTree::create(num_symbols),
+            tree: AdaptiveHuffmanTree::create(max_freq, num_symbols),
             bits: BitVec::new(),
             ptr: 0
         }
@@ -356,9 +356,9 @@ impl AdaptiveHuffmanCoder {
 }
 
 impl AdaptiveHuffmanDecoder {
-    pub fn create(num_symbols: usize) -> Self {
+    pub fn create(max_freq: usize, num_symbols: usize) -> Self {
         Self {
-            tree: AdaptiveHuffmanTree::create(num_symbols),
+            tree: AdaptiveHuffmanTree::create(max_freq, num_symbols),
             bits: BitVec::new(),
             ptr: 0
         }