RSO: `make` command (#67)

Allow to create rso file from relocatable elf

No sel file support yet

README.md

@@ -39,6 +39,7 @@ project structure and build system that uses decomp-toolkit under the hood.
   - [rel info](#rel-info)
   - [rel merge](#rel-merge)
   - [rso info](#rso-info)
+  - [rso make](#rso-make)
   - [shasum](#shasum)
   - [nlzss decompress](#nlzss-decompress)
   - [rarc list](#rarc-list)
@@ -370,6 +371,22 @@ Prints information about an RSO file.
 $ dtk rso info input.rso
 ```
 
+### rso make
+
+> [!WARNING]  
+> This command does not yet support creating SEL files.
+
+Creates an RSO file from a relocatable ELF file.
+
+Options:
+- `-o`, `--output <File>`: Output RSO file.
+- `-m`, `--module-name <Name>`: Module name (or path). Default: input name
+- `-e`, `--export <File>`: File containing exported symbol names. (Newline separated)
+
+```shell
+$ dtk rso make input.elf -o input.rso
+```
+
 ### shasum
 
 Calculate and verify SHA-1 hashes.

src/cmd/rso.rs

@@ -1,9 +1,24 @@
-use std::path::PathBuf;
+use std::{
+    io::{BufRead, Seek, Write},
+    path::{Path, PathBuf},
+};
 
-use anyhow::Result;
+use anyhow::{bail, ensure, Context, Result};
 use argp::FromArgs;
+use object::{
+    elf::{R_PPC_NONE, R_PPC_REL24},
+    Architecture, Endianness, Object, ObjectKind, ObjectSection, ObjectSymbol, SectionKind,
+    SymbolIndex, SymbolKind, SymbolSection,
+};
 
-use crate::util::{file::map_file, rso::process_rso};
+use crate::util::{
+    file::{buf_reader, buf_writer, map_file},
+    reader::{Endian, ToWriter},
+    rso::{
+        process_rso, symbol_hash, RsoHeader, RsoRelocation, RsoSectionHeader, RsoSymbol,
+        RSO_SECTION_NAMES,
+    },
+};
 
 #[derive(FromArgs, PartialEq, Debug)]
 /// Commands for processing RSO files.
@@ -17,6 +32,7 @@ pub struct Args {
 #[argp(subcommand)]
 enum SubCommand {
     Info(InfoArgs),
+    Make(MakeArgs),
 }
 
 #[derive(FromArgs, PartialEq, Eq, Debug)]
@@ -28,9 +44,31 @@ pub struct InfoArgs {
     rso_file: PathBuf,
 }
 
+#[derive(FromArgs, PartialEq, Eq, Debug)]
+/// Creates an RSO from an ELF.
+#[argp(subcommand, name = "make")]
+pub struct MakeArgs {
+    #[argp(positional, arg_name = "ELF File")]
+    /// elf file
+    input: PathBuf,
+
+    #[argp(option, short = 'o', arg_name = "File")]
+    /// output file path
+    output: PathBuf,
+
+    #[argp(option, short = 'm', arg_name = "Name")]
+    /// module name (or path). Default: input name
+    module_name: Option<String>,
+
+    #[argp(option, short = 'e', arg_name = "File")]
+    /// file containing exported symbol names (newline separated)
+    export: Option<PathBuf>,
+}
+
 pub fn run(args: Args) -> Result<()> {
     match args.command {
         SubCommand::Info(c_args) => info(c_args),
+        SubCommand::Make(c_args) => make(c_args),
     }
 }
 
@@ -44,3 +82,436 @@ fn info(args: InfoArgs) -> Result<()> {
     println!("Read RSO module {}", rso.name);
     Ok(())
 }
+
+fn make(args: MakeArgs) -> Result<()> {
+    let file = map_file(&args.input)?;
+    let obj_file = object::read::File::parse(file.as_slice())?;
+    match obj_file.architecture() {
+        Architecture::PowerPc => {}
+        arch => bail!("Unexpected architecture: {arch:?}"),
+    };
+    ensure!(obj_file.endianness() == Endianness::Big, "Expected big endian");
+
+    let module_name = match args.module_name {
+        Some(n) => n,
+        None => args.input.display().to_string(),
+    };
+
+    let symbols_to_export = match args.export {
+        Some(export_file_path) => {
+            let export_file_reader = buf_reader(export_file_path)?;
+            export_file_reader.lines().map_while(Result::ok).collect()
+        }
+        None => vec![],
+    };
+
+    match obj_file.kind() {
+        ObjectKind::Executable => {
+            make_sel(obj_file, &args.output, &module_name, symbols_to_export)?
+        }
+        ObjectKind::Relocatable => {
+            make_rso(obj_file, &args.output, &module_name, symbols_to_export)?
+        }
+        kind => bail!("Unexpected ELF type: {kind:?}"),
+    }
+
+    Ok(())
+}
+
+fn make_sel<P: AsRef<Path>>(
+    _file: object::File,
+    _output: P,
+    _module_name: &str,
+    _symbols_to_export: Vec<String>,
+) -> Result<()> {
+    bail!("Creating SEL files is not supported yet.");
+}
+
+fn make_rso<P: AsRef<Path>>(
+    file: object::File,
+    output: P,
+    module_name: &str,
+    symbols_to_export: Vec<String>,
+) -> Result<()> {
+    let mut out = buf_writer(output)?;
+
+    let try_populate_symbol_index_and_offset =
+        |name: &str, index: &mut u8, offset: &mut u32| -> Result<()> {
+            let Some(sym) = file.symbol_by_name(name) else {
+                return Ok(());
+            };
+
+            let si = sym
+                .section_index()
+                .with_context(|| format!("Failed to find symbol `{}` section index", name))?;
+            let addr = sym.address();
+
+            *index = si.0 as u8;
+            *offset = addr as u32;
+
+            Ok(())
+        };
+
+    let pad_to_alignment =
+        |out: &mut std::io::BufWriter<std::fs::File>, alignment: u64| -> Result<()> {
+            if alignment == 0 {
+                return Ok(());
+            }
+
+            const ZERO_BUF: [u8; 32] = [0u8; 32];
+            let pos = out.stream_position()?;
+            let mut count = (!(alignment - 1) & ((alignment + pos) - 1)) - pos;
+
+            while count > 0 {
+                let slice_size = std::cmp::min(ZERO_BUF.len(), count as usize);
+                out.write_all(&ZERO_BUF[0..slice_size])?;
+                count -= slice_size as u64;
+            }
+
+            Ok(())
+        };
+
+    let mut header = RsoHeader::new();
+
+    try_populate_symbol_index_and_offset(
+        "_prolog",
+        &mut header.prolog_section,
+        &mut header.prolog_offset,
+    )?;
+    try_populate_symbol_index_and_offset(
+        "_epilog",
+        &mut header.epilog_section,
+        &mut header.epilog_offset,
+    )?;
+    try_populate_symbol_index_and_offset(
+        "_unresolved",
+        &mut header.unresolved_section,
+        &mut header.unresolved_offset,
+    )?;
+
+    header.to_writer(&mut out, Endian::Big)?;
+    header.section_info_offset = out.stream_position()? as u32;
+    {
+        // Write Sections Info Table (Blank)
+        let blank_section = RsoSectionHeader::default();
+        for _ in file.sections() {
+            header.num_sections += 1;
+            blank_section.to_writer(&mut out, Endian::Big)?;
+        }
+    }
+
+    let mut rso_sections: Vec<RsoSectionHeader> = vec![];
+    for section in file.sections() {
+        let is_valid_section =
+            section.name().is_ok_and(|n| RSO_SECTION_NAMES.iter().any(|&s| s == n));
+        let section_size = section.size();
+
+        if !is_valid_section || section_size == 0 {
+            rso_sections.push(RsoSectionHeader::default());
+            continue;
+        }
+
+        if section.kind() == SectionKind::UninitializedData {
+            header.bss_size += section_size as u32;
+            rso_sections.push(RsoSectionHeader { offset_and_flags: 0, size: section_size as u32 });
+            continue;
+        }
+
+        pad_to_alignment(&mut out, section.align())?;
+        let section_offset_in_file = out.stream_position()?;
+        let section_data = section.data()?;
+        out.write_all(section_data)?;
+        rso_sections.push(RsoSectionHeader {
+            offset_and_flags: section_offset_in_file as u32,
+            size: section_size as u32,
+        });
+    }
+
+    pad_to_alignment(&mut out, 4)?;
+    header.name_offset = out.stream_position()? as u32;
+
+    // Rewind and write the correct section info table
+    out.seek(std::io::SeekFrom::Start(header.section_info_offset as u64))?;
+    for section in &rso_sections {
+        section.to_writer(&mut out, Endian::Big)?;
+    }
+
+    // Write the module name
+    out.seek(std::io::SeekFrom::Start(header.name_offset as u64))?;
+
+    let module_name = module_name.as_bytes();
+    out.write_all(module_name)?;
+    header.name_size = module_name.len() as u32;
+
+    // Accumulate exported and imported symbol
+    let mut import_symbol_table: Vec<RsoSymbol> = vec![];
+    let mut export_symbol_table: Vec<RsoSymbol> = vec![];
+    for symbol in file.symbols() {
+        let sym_binding = match symbol.flags() {
+            object::SymbolFlags::Elf { st_info, st_other: _ } => st_info >> 4,
+            flag => bail!("Unknown symbol flag found `{:?}`", flag),
+        };
+
+        let symbol_name = match symbol.name() {
+            Ok(n) => {
+                if n.is_empty() {
+                    continue;
+                }
+
+                n
+            }
+            Err(_) => continue,
+        };
+
+        // In the [`RsoSymbol::name_offset`] field we would store the symbol index temp
+        match symbol.section_index() {
+            Some(section_index)
+                if sym_binding != object::elf::STB_LOCAL && section_index.0 != 0 =>
+            {
+                // Symbol to export
+                if !symbols_to_export.iter().any(|s| s == symbol_name) {
+                    continue;
+                }
+
+                let hash = symbol_hash(symbol_name);
+                export_symbol_table.push(RsoSymbol {
+                    name_offset: symbol.index().0 as u32,
+                    offset: symbol.address() as u32,
+                    section_index: section_index.0 as u32,
+                    hash: Some(hash),
+                });
+            }
+            None => {
+                if matches!(symbol.kind(), SymbolKind::File) {
+                    continue;
+                }
+
+                if symbol.section() == SymbolSection::Absolute {
+                    if !symbols_to_export.iter().any(|s| s == symbol_name) {
+                        continue;
+                    }
+
+                    // Special Symbols
+                    let hash = symbol_hash(symbol_name);
+                    export_symbol_table.push(RsoSymbol {
+                        name_offset: symbol.index().0 as u32,
+                        offset: symbol.address() as u32,
+                        section_index: 0xFFF1_u32,
+                        hash: Some(hash),
+                    });
+                    continue;
+                }
+
+                // Symbol to import
+                import_symbol_table.push(RsoSymbol {
+                    name_offset: symbol.index().0 as u32,
+                    offset: symbol.address() as u32,
+                    section_index: 0, // Relocation offset
+                    hash: None,
+                });
+            }
+            _ => continue,
+        }
+    }
+
+    // Accumulate relocations
+    let mut imported_relocations: Vec<RsoRelocation> = vec![];
+    let mut exported_relocations: Vec<RsoRelocation> = vec![];
+
+    for section in file.sections() {
+        let is_valid_section =
+            section.name().is_ok_and(|n| RSO_SECTION_NAMES.iter().any(|&s| s == n));
+        if !is_valid_section {
+            continue;
+        }
+
+        let relocation_section_idx = section.index().0 as u32;
+        let relocation_section_offset =
+            rso_sections[relocation_section_idx as usize].offset_and_flags;
+
+        for (reloc_addr, reloc) in section.relocations() {
+            let reloc_target_symbol_idx = match reloc.target() {
+                object::RelocationTarget::Symbol(t) => t,
+                _ => continue,
+            };
+
+            let Ok(reloc_target_symbol) = file.symbol_by_index(reloc_target_symbol_idx) else {
+                bail!(
+                    "Failed to find relocation `{:08X}` symbol ({})",
+                    reloc_addr,
+                    reloc_target_symbol_idx.0
+                );
+            };
+
+            let reloc_type = match reloc.flags() {
+                object::RelocationFlags::Elf { r_type } => r_type,
+                _ => continue,
+            };
+
+            if reloc_type == R_PPC_NONE {
+                continue;
+            }
+
+            match reloc_target_symbol.section_index() {
+                None => {
+                    // Imported symbol relocation
+                    // Get the symbol index inside the import symbol table
+                    let symbol_table_idx = match import_symbol_table
+                        .iter()
+                        .position(|s| s.name_offset == reloc_target_symbol_idx.0 as u32)
+                    {
+                        Some(idx) => idx,
+                        // We should always find the symbol. If not, it means a logic error in the symbol accumulator loop
+                        // panic?
+                        None => {
+                            bail!("Failed to find imported symbol in the accumulated symbol table.")
+                        }
+                    };
+
+                    let id_and_type = ((symbol_table_idx as u32) << 8) | (reloc_type & 0xFF);
+                    imported_relocations.push(RsoRelocation {
+                        // Convert the relocation offset from being section relative to file relative
+                        offset: relocation_section_offset + reloc_addr as u32,
+                        id_and_type,
+                        target_offset: 0,
+                    });
+                }
+                Some(reloc_symbol_section_idx) => {
+                    // Exported symbol relocation
+                    let id_and_type =
+                        ((reloc_symbol_section_idx.0 as u32) << 8) | (reloc_type & 0xFF);
+                    exported_relocations.push(RsoRelocation {
+                        // Convert the relocation offset from being section relative to file relative
+                        offset: relocation_section_offset + reloc_addr as u32,
+                        id_and_type,
+                        target_offset: reloc.addend() as u32 + reloc_target_symbol.address() as u32,
+                    });
+                }
+            }
+
+            // Apply relocation with the `_unresolved` as the symbol, if the module export the function
+            if reloc_type == R_PPC_REL24
+                && header.unresolved_offset != 0
+                && header.unresolved_section == relocation_section_idx as u8
+            {
+                let target_section = file
+                    .section_by_index(object::SectionIndex(relocation_section_idx as usize))
+                    .unwrap();
+                let target_section_data = target_section.data().unwrap();
+
+                // Copy instruction
+                let mut intruction_buff = [0u8; 4];
+                intruction_buff.copy_from_slice(
+                    &target_section_data[(reloc_addr as usize)..(reloc_addr + 4) as usize],
+                );
+                let target_instruction = u32::from_be_bytes(intruction_buff);
+
+                let off_diff = header.unresolved_offset as i64 - reloc_addr as i64;
+                let replacement_instruction =
+                    (off_diff as u32 & 0x3fffffcu32) | (target_instruction & 0xfc000003u32);
+                let intruction_buff = replacement_instruction.to_be_bytes();
+
+                let relocation_file_offset = relocation_section_offset as u64 + reloc_addr;
+                let current_stream_pos = out.stream_position()?;
+                out.seek(std::io::SeekFrom::Start(relocation_file_offset))?;
+                out.write_all(&intruction_buff)?;
+                out.seek(std::io::SeekFrom::Start(current_stream_pos))?;
+            }
+        }
+    }
+
+    // Sort imported relocation, by symbol index
+    imported_relocations.sort_by(|lhs, rhs| {
+        let lhs_symbol_idx = lhs.id();
+        let rhs_symbol_idx = rhs.id();
+        rhs_symbol_idx.cmp(&lhs_symbol_idx)
+    });
+
+    // Sort Export Symbol by Hash
+    export_symbol_table.sort_by(|lhs, rhs| rhs.hash.unwrap().cmp(&lhs.hash.unwrap()));
+
+    {
+        // Write Export Symbol Table
+        pad_to_alignment(&mut out, 4)?;
+        header.export_table_offset = out.stream_position()? as u32;
+        header.export_table_size = (export_symbol_table.len() * 16) as u32;
+
+        let mut export_symbol_name_table: Vec<u8> = vec![];
+        for export_symbol in &mut export_symbol_table {
+            let export_elf_symbol =
+                file.symbol_by_index(SymbolIndex(export_symbol.name_offset as usize)).unwrap();
+            let export_elf_symbol_name = export_elf_symbol.name().unwrap();
+            export_symbol.name_offset = export_symbol_name_table.len() as u32;
+            export_symbol.to_writer(&mut out, Endian::Big)?;
+
+            export_symbol_name_table.extend_from_slice(export_elf_symbol_name.as_bytes());
+            export_symbol_name_table.push(0u8); // '\0'
+        }
+
+        // Write Export Symbol Name Table
+        pad_to_alignment(&mut out, 4)?;
+        header.export_table_name_offset = out.stream_position()? as u32;
+        out.write_all(&export_symbol_name_table)?;
+    }
+
+    {
+        // Write Imported Symbol Relocation
+        pad_to_alignment(&mut out, 4)?;
+        header.external_rel_offset = out.stream_position()? as u32;
+        header.external_rel_size = (imported_relocations.len() * 12) as u32;
+
+        for reloc in &imported_relocations {
+            reloc.to_writer(&mut out, Endian::Big)?;
+        }
+    }
+
+    {
+        pad_to_alignment(&mut out, 4)?;
+        header.import_table_offset = out.stream_position()? as u32;
+        header.import_table_size = (import_symbol_table.len() * 12) as u32;
+
+        let mut import_symbol_name_table: Vec<u8> = vec![];
+
+        for (import_symbol_idx, import_symbol) in import_symbol_table.iter_mut().enumerate() {
+            let import_elf_symbol_idx = import_symbol.name_offset as usize;
+            let import_elf_symbol =
+                file.symbol_by_index(SymbolIndex(import_elf_symbol_idx)).unwrap();
+            let import_elf_symbol_name = import_elf_symbol.name().unwrap();
+            import_symbol.name_offset = import_symbol_name_table.len() as u32;
+
+            // Gather the index of the first relocation that utilize this symbol
+            let first_relocation_offset = imported_relocations
+                .iter()
+                .position(|r| r.id() == import_symbol_idx as u32)
+                .map(|idx| idx * 12)
+                .unwrap_or(usize::MAX) as u32;
+            import_symbol.section_index = first_relocation_offset;
+            import_symbol.to_writer(&mut out, Endian::Big)?;
+
+            import_symbol_name_table.extend_from_slice(import_elf_symbol_name.as_bytes());
+            import_symbol_name_table.push(0u8); // '\0'
+        }
+
+        // Write Export Symbol Name Table
+        pad_to_alignment(&mut out, 4)?;
+        header.import_table_name_offset = out.stream_position()? as u32;
+        out.write_all(&import_symbol_name_table)?;
+    }
+
+    {
+        // Write Internal Relocation Table
+        pad_to_alignment(&mut out, 4)?;
+        header.internal_rel_offset = out.stream_position()? as u32;
+        header.internal_rel_size = (exported_relocations.len() * 12) as u32;
+
+        for reloc in &exported_relocations {
+            reloc.to_writer(&mut out, Endian::Big)?;
+        }
+    }
+
+    pad_to_alignment(&mut out, 32)?;
+    out.seek(std::io::SeekFrom::Start(0))?;
+    header.to_writer(&mut out, Endian::Big)?;
+
+    Ok(())
+}

src/util/rso.rs

@@ -34,11 +34,16 @@ pub const DOL_SECTION_NAMES: [Option<&str>; 14] = [
     Some(".sbss2"),
     None, // s_zero2
 ];
+
+pub const RSO_SECTION_NAMES: [&str; 7] =
+    [".init", ".text", ".ctors", ".dtors", ".rodata", ".data", ".bss"];
+
 /// extabindex section index.
 pub const DOL_SECTION_ETI: u32 = 241;
 /// ABS symbol section index.
 pub const DOL_SECTION_ABS: u32 = 65521;
 
+#[derive(Default)]
 pub struct RsoHeader {
     // Pointer to the next module, forming a linked list. Always 0, filled in at runtime.
     // pub next: u32,
@@ -101,6 +106,10 @@ pub struct RsoHeader {
     pub import_table_name_offset: u32,
 }
 
+impl RsoHeader {
+    pub fn new() -> Self { Self { version: 1, ..Default::default() } }
+}
+
 impl FromReader for RsoHeader {
     type Args = ();
 
@@ -205,13 +214,46 @@ impl FromReader for RsoHeader {
     }
 }
 
-#[derive(Copy, Clone, Debug)]
+impl ToWriter for RsoHeader {
+    fn to_writer<W>(&self, writer: &mut W, e: Endian) -> io::Result<()>
+    where W: Write + ?Sized {
+        (0u64).to_writer(writer, e)?; // next and prev
+        self.num_sections.to_writer(writer, e)?;
+        self.section_info_offset.to_writer(writer, e)?;
+        self.name_offset.to_writer(writer, e)?;
+        self.name_size.to_writer(writer, e)?;
+        self.version.to_writer(writer, e)?;
+        self.bss_size.to_writer(writer, e)?;
+        self.prolog_section.to_writer(writer, e)?;
+        self.epilog_section.to_writer(writer, e)?;
+        self.unresolved_section.to_writer(writer, e)?;
+        (0u8).to_writer(writer, e)?; // bss_section
+        self.prolog_offset.to_writer(writer, e)?;
+        self.epilog_offset.to_writer(writer, e)?;
+        self.unresolved_offset.to_writer(writer, e)?;
+        self.internal_rel_offset.to_writer(writer, e)?;
+        self.internal_rel_size.to_writer(writer, e)?;
+        self.external_rel_offset.to_writer(writer, e)?;
+        self.external_rel_size.to_writer(writer, e)?;
+        self.export_table_offset.to_writer(writer, e)?;
+        self.export_table_size.to_writer(writer, e)?;
+        self.export_table_name_offset.to_writer(writer, e)?;
+        self.import_table_offset.to_writer(writer, e)?;
+        self.import_table_size.to_writer(writer, e)?;
+        self.import_table_name_offset.to_writer(writer, e)?;
+        Ok(())
+    }
+
+    fn write_size(&self) -> usize { Self::STATIC_SIZE }
+}
+
+#[derive(Copy, Clone, Debug, Default)]
 pub struct RsoSectionHeader {
     /// Absolute offset of the section.
     /// The lowest bit is set if the section is executable.
-    offset_and_flags: u32,
+    pub offset_and_flags: u32,
     /// Size of the section.
-    size: u32,
+    pub size: u32,
 }
 
 impl FromReader for RsoSectionHeader {
@@ -255,17 +297,17 @@ impl RsoSectionHeader {
     pub fn exec(&self) -> bool { self.offset_and_flags & 1 != 0 }
 }
 
-struct RsoRelocation {
+pub struct RsoRelocation {
     /// Absolute offset of this relocation (relative to the start of the RSO file).
-    offset: u32,
+    pub offset: u32,
     /// For internal relocations, this is the section index of the symbol being patched to.
     /// For external relocations, this is the index of the symbol within the import symbol table.
     /// The lowest 8 bits are the relocation type.
-    id_and_type: u32,
+    pub id_and_type: u32,
     /// For internal relocations, this is the section-relative offset of the target symbol.
     /// For external relocations, this is unused and always 0 (the offset is calculated using the
     /// import symbol table).
-    target_offset: u32,
+    pub target_offset: u32,
 }
 
 impl FromReader for RsoRelocation {
@@ -315,22 +357,23 @@ impl RsoRelocation {
 }
 
 #[derive(Copy, Clone, Debug, PartialEq, Eq)]
-enum RsoSymbolKind {
+pub enum RsoSymbolKind {
     Import,
     Export,
 }
 
-struct RsoSymbol {
+#[derive(Debug)]
+pub struct RsoSymbol {
     /// Relative offset into the name table pointed to in the header,
     /// which points to the name of this symbol.
-    name_offset: u32,
+    pub name_offset: u32,
     /// The section-relative offset to the symbol. This is always 0 for imports.
-    offset: u32,
+    pub offset: u32,
     /// For exports, index of the section that contains this symbol.
-    /// For imports, appears to be an offset?
+    /// For imports, offset of the first relocation that use this symbol
-    section_index: u32,
+    pub section_index: u32,
     /// A hash of the symbol name. Only present for exports.
-    hash: Option<u32>,
+    pub hash: Option<u32>,
 }
 
 impl FromReader for RsoSymbol {
@@ -360,7 +403,8 @@ impl ToWriter for RsoSymbol {
         self.offset.to_writer(writer, e)?;
         self.section_index.to_writer(writer, e)?;
         if let Some(hash) = self.hash {
-            hash.to_writer(writer, e)?;
+            // Since the nature of the value is not numeric, we must preserve the order of the bytes
+            writer.write_all(&hash.to_ne_bytes())?;
         }
         Ok(())
     }
@@ -524,7 +568,7 @@ where R: Read + Seek + ?Sized {
     Ok(obj)
 }
 
-fn symbol_hash(s: &str) -> u32 {
+pub fn symbol_hash(s: &str) -> u32 {
     s.bytes().fold(0u32, |hash, c| {
         let mut m = (hash << 4).wrapping_add(c as u32);
         let n = m & 0xF0000000;