From 698f8c2f01ea549d77d7dc3338a12e04c11057b9 Mon Sep 17 00:00:00 2001
From: Daniel Baumann <daniel.baumann@progress-linux.org>
Date: Wed, 17 Apr 2024 14:02:58 +0200
Subject: Adding upstream version 1.64.0+dfsg1.

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
---
 vendor/snap/build.rs | 124 +++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 124 insertions(+)
 create mode 100644 vendor/snap/build.rs

(limited to 'vendor/snap/build.rs')

diff --git a/vendor/snap/build.rs b/vendor/snap/build.rs
new file mode 100644
index 000000000..283164f2e
--- /dev/null
+++ b/vendor/snap/build.rs
@@ -0,0 +1,124 @@
+use std::env;
+use std::fs::File;
+use std::io::{self, Write};
+use std::path::{Path, PathBuf};
+
+const CASTAGNOLI_POLY: u32 = 0x82f63b78;
+
+type Result<T> = std::result::Result<T, Box<dyn std::error::Error>>;
+
+fn main() {
+    if let Err(err) = try_main() {
+        panic!("{}", err);
+    }
+}
+
+fn try_main() -> Result<()> {
+    let out_dir = match env::var_os("OUT_DIR") {
+        None => {
+            return Err(From::from("OUT_DIR environment variable not defined"))
+        }
+        Some(out_dir) => PathBuf::from(out_dir),
+    };
+    write_tag_lookup_table(&out_dir)?;
+    write_crc_tables(&out_dir)?;
+    Ok(())
+}
+
+fn write_tag_lookup_table(out_dir: &Path) -> Result<()> {
+    let out_path = out_dir.join("tag.rs");
+    let mut out = io::BufWriter::new(File::create(out_path)?);
+
+    writeln!(out, "pub const TAG_LOOKUP_TABLE: [u16; 256] = [")?;
+    for b in 0u8..=255 {
+        writeln!(out, "    {},", tag_entry(b))?;
+    }
+    writeln!(out, "];")?;
+    Ok(())
+}
+
+fn tag_entry(b: u8) -> u16 {
+    let b = b as u16;
+    match b & 0b00000011 {
+        0b00 => {
+            let lit_len = (b >> 2) + 1;
+            if lit_len <= 60 {
+                lit_len
+            } else {
+                assert!(lit_len <= 64);
+                (lit_len - 60) << 11
+            }
+        }
+        0b01 => {
+            let len = 4 + ((b >> 2) & 0b111);
+            let offset = (b >> 5) & 0b111;
+            (1 << 11) | (offset << 8) | len
+        }
+        0b10 => {
+            let len = 1 + (b >> 2);
+            (2 << 11) | len
+        }
+        0b11 => {
+            let len = 1 + (b >> 2);
+            (4 << 11) | len
+        }
+        _ => unreachable!(),
+    }
+}
+
+fn write_crc_tables(out_dir: &Path) -> Result<()> {
+    let out_path = out_dir.join("crc32_table.rs");
+    let mut out = io::BufWriter::new(File::create(out_path)?);
+
+    let table = make_table(CASTAGNOLI_POLY);
+    let table16 = make_table16(CASTAGNOLI_POLY);
+
+    writeln!(out, "pub const TABLE: [u32; 256] = [")?;
+    for &x in table.iter() {
+        writeln!(out, "    {},", x)?;
+    }
+    writeln!(out, "];\n")?;
+
+    writeln!(out, "pub const TABLE16: [[u32; 256]; 16] = [")?;
+    for table in table16.iter() {
+        writeln!(out, "    [")?;
+        for &x in table.iter() {
+            writeln!(out, "        {},", x)?;
+        }
+        writeln!(out, "    ],")?;
+    }
+    writeln!(out, "];")?;
+
+    out.flush()?;
+
+    Ok(())
+}
+
+fn make_table16(poly: u32) -> [[u32; 256]; 16] {
+    let mut tab = [[0; 256]; 16];
+    tab[0] = make_table(poly);
+    for i in 0..256 {
+        let mut crc = tab[0][i];
+        for j in 1..16 {
+            crc = (crc >> 8) ^ tab[0][crc as u8 as usize];
+            tab[j][i] = crc;
+        }
+    }
+    tab
+}
+
+fn make_table(poly: u32) -> [u32; 256] {
+    let mut tab = [0; 256];
+    for i in 0u32..256u32 {
+        let mut crc = i;
+        for _ in 0..8 {
+            if crc & 1 == 1 {
+                crc = (crc >> 1) ^ poly;
+            } else {
+                crc >>= 1;
+            }
+        }
+        tab[i as usize] = crc;
+    }
+    tab
+}
-- 
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