0.3.0: fix linkage in C mode

.gitignore

@@ -1,2 +1,5 @@
 # Cargo
 target/
+
+# Slop
+.vscode/

Cargo.lock

@@ -4,7 +4,7 @@ version = 4
 
 [[package]]
 name = "bin2hpp"
-version = "0.2.3"
+version = "0.3.0"
 dependencies = [
  "thiserror",
 ]

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "bin2hpp"
-version = "0.2.3"
+version = "0.3.0"
 authors = ["Adam Macdonald"]
 edition = "2024"
 license = "GPL-3.0-only"

README.md

@@ -6,24 +6,52 @@ CLI tool for converting files into header files which one can use to directly em
 
 ## Building
 
-1. `cargo build`
+`cargo build`, or `cargo [build | run | install] --profile optimised` to build an optimised binary.
+
+The performance (but potentially not the executable size) can be further optimised by telling the compiler to use a more modern instruction set: `RUSTFLAGS="-C target-cpu=native"`.
 
 ## Usage
 
 ### Basic usage
 
-`$ bin2hpp -i ~/my_image.bmp` will generate an `my_image_bmp.h` file in your current working directory containing something similar to the following:
+`$ bin2hpp -i my_library.dll -o c_header.h` will generate a `c_header.h` file in your current working directory containing something similar to the following:
 
 ```c
-// Generated by bin2hpp 0.2.0
-#ifndef MY_IMAGE_BMP_H
-#define MY_IMAGE_BMP_H
-#include <stddef.h>
-const size_t MYIMAGE_BMP_LEN = 36000054;
-const unsigned char MYIMAGE_BMP[MYIMAGE_BMP_LEN] = {0x42,0x4d,0x36,0x51,0x25, ...}
+// Generated by bin2hpp 0.3.0
+#ifdef MY_LIBRARY_DLL_INIT
+#define MY_LIBRARY_DLL_LEN 9728
+const unsigned char MY_LIBRARY_DLL[MY_LIBRARY_DLL_LEN] = {77,90,144,0,3,0,0,0,4, ...};
 #else
-extern const size_t MYIMAGE_BMP_LEN;
-extern const unsigned char MYIMAGE_BMP[MYIMAGE_BMP_LEN];
+#define MY_LIBRARY_DLL_LEN 9728
+extern const unsigned char MY_LIBRARY_DLL[MY_LIBRARY_DLL_LEN];
+#endif
+```
+
+Note how in **C mode** one must `#define MY_LIBRARY_DLL_INIT`, or whatever the corresponding implementation macro is for your generated header file, in exactly _one_ C source file (`*.c`, not in a `*.h` file).
+
+Example:
+
+`main.c`
+```c
+// In any other C source files other than the first: do not redefine
+#define MY_LIBRARY_DLL_INIT
+#include "c_header.h"
+
+int main() {
+    return MY_LIBRARY_DLL_LEN;
+}
+```
+
+Alternatively, in **C++ mode**: `bin2hpp -i my_library.dll -o cpp_header.hpp --cpp --constexpr --stdarray --i8`
+
+```cpp
+// Generated by bin2hpp 0.3.0
+#if !defined(CPP_HEADER_HPP)
+#define CPP_HEADER_HPP
+#include <cstdint>
+#include <array>
+#define MY_LIBRARY_DLL_LEN 9728
+inline constexpr std::array<std::int8_t,MY_LIBRARY_DLL_LEN> MY_LIBRARY_DLL = {77,90,-112,0,3,0,0,0,4, ...};
 #endif
 ```
 

src/cfg.rs

@@ -22,7 +22,8 @@ pub struct Config {
     pub(crate) constness: Constness,
     pub(crate) symbol_name: String,
     pub(crate) namespace: Option<String>,
-    pub(crate) guard_name: String,
+    pub(crate) impl_macro: String,
+    pub(crate) header_guard: String,
     pub(crate) container_type: ContainerType,
 }
 
@@ -56,6 +57,54 @@ pub fn parse_config_from_args(args: &CliArgs) -> Result<Config, ProgramConfigErr
         }
     };
 
+    let symbol_name = match &args.symbol_name {
+        Some(s) => {
+            if s.chars().all(|c| c.is_ascii_alphanumeric() || c == '_') {
+                s.to_string()
+            } else {
+                return Err(ProgramConfigError::InvalidSymbolName(s.to_string()));
+            }
+        }
+        _ => {
+            let mut stem: String = match args.input_file_path.file_stem() {
+                Some(s) => s.to_string_lossy().to_string(),
+                None => {
+                    return Err(ProgramConfigError::InvalidPath(
+                        args.input_file_path.to_string_lossy().to_string(),
+                    ));
+                }
+            };
+            stem.retain(|c| c.is_ascii_alphanumeric() || c == '_');
+
+            let mut ext: String = match args.input_file_path.extension() {
+                Some(s) => format!("_{}", s.to_string_lossy()),
+                None => "".to_string(),
+            };
+            ext.retain(|c| c.is_ascii_alphanumeric() || c == '_');
+
+            format!("{}{}", stem.to_ascii_uppercase(), ext.to_ascii_uppercase())
+        }
+    };
+
+    let header_guard = match output_path.file_stem() {
+        Some(stem) => {
+            format!(
+                "{}_{}",
+                stem.to_string_lossy().to_uppercase(),
+                if let Some(ext) = output_path.extension() {
+                    ext.to_string_lossy().to_uppercase()
+                } else {
+                    "".into()
+                }
+            )
+        }
+        None => {
+            return Err(ProgramConfigError::InvalidPath(
+                output_path.to_string_lossy().to_string(),
+            ));
+        }
+    };
+
     Ok(Config {
         input_file_path: args.input_file_path.clone(),
         output_file_path: output_path.clone(),
@@ -67,34 +116,7 @@ pub fn parse_config_from_args(args: &CliArgs) -> Result<Config, ProgramConfigErr
         },
         language: args.language,
         constness: args.constness,
-        symbol_name: match &args.symbol_name {
-            Some(s) => {
-                if s.chars().all(|c| c.is_ascii_alphanumeric() || c == '_') {
-                    s.to_string()
-                } else {
-                    return Err(ProgramConfigError::InvalidSymbolName(s.to_string()));
-                }
-            }
-            _ => {
-                let mut stem: String = match args.input_file_path.file_stem() {
-                    Some(s) => s.to_string_lossy().to_string(),
-                    None => {
-                        return Err(ProgramConfigError::InvalidPath(
-                            args.input_file_path.to_string_lossy().to_string(),
-                        ));
-                    }
-                };
-                stem.retain(|c| c.is_ascii_alphanumeric());
-
-                let mut ext: String = match args.input_file_path.extension() {
-                    Some(s) => format!("_{}", s.to_string_lossy()),
-                    None => "".to_string(),
-                };
-                ext.retain(|c| c.is_ascii_alphanumeric());
-
-                format!("{}{}", stem.to_ascii_uppercase(), ext.to_ascii_uppercase())
-            }
-        },
+        symbol_name: symbol_name.clone(),
         namespace: match &args.namespace {
             Some(ns) => {
                 if ns.chars().all(|c| c.is_ascii_alphanumeric() || c == '_') {
@@ -105,7 +127,7 @@ pub fn parse_config_from_args(args: &CliArgs) -> Result<Config, ProgramConfigErr
             }
             _ => None,
         },
-        guard_name: match &args.guard_name {
+        impl_macro: match &args.impl_macro_name {
             Some(guard) => {
                 if guard.chars().all(|c| c.is_ascii_alphanumeric() || c == '_') {
                     guard.clone()
@@ -114,29 +136,10 @@ pub fn parse_config_from_args(args: &CliArgs) -> Result<Config, ProgramConfigErr
                 }
             }
             _ => {
-                let mut stem: String = match output_path.file_stem() {
-                    Some(s) => s.to_string_lossy().to_ascii_uppercase(),
-                    None => {
-                        return Err(ProgramConfigError::InvalidPath(
-                            args.input_file_path.to_string_lossy().to_string(),
-                        ));
-                    }
-                };
-                stem.retain(|c| c.is_ascii_alphanumeric() || c == '_');
-
-                let mut ext: String = match output_path.extension() {
-                    Some(s) => s.to_string_lossy().to_ascii_uppercase(),
-                    None => {
-                        return Err(ProgramConfigError::InvalidPath(
-                            args.input_file_path.to_string_lossy().to_string(),
-                        ));
-                    }
-                };
-                ext.retain(|c| c.is_ascii_alphanumeric());
-
-                format!("{}_{}", stem, ext)
+                format!("{}_INIT", symbol_name.to_uppercase())
             }
         },
+        header_guard: header_guard,
         container_type: args.container_type,
     })
 }

src/cli.rs

@@ -20,6 +20,26 @@ pub enum ByteType {
     I8,
 }
 
+impl ByteType {
+    pub fn to_c_type(&self) -> &'static str {
+        match self {
+            ByteType::UnsignedChar => "unsigned char",
+            ByteType::Char => "char",
+            ByteType::U8 => "uint8_t",
+            ByteType::I8 => "int8_t",
+        }
+    }
+
+    pub fn to_cpp_type(&self) -> &'static str {
+        match self {
+            ByteType::UnsignedChar => self.to_c_type(),
+            ByteType::Char => self.to_c_type(),
+            ByteType::U8 => "std::uint8_t",
+            ByteType::I8 => "std::int8_t",
+        }
+    }
+}
+
 #[derive(Debug, PartialEq, Clone, Copy)]
 pub enum ContainerType {
     CArray(ByteType),
@@ -61,7 +81,7 @@ pub struct CliArgs {
     pub(crate) constness: Constness,
     pub(crate) symbol_name: Option<String>,
     pub(crate) namespace: Option<String>,
-    pub(crate) guard_name: Option<String>,
+    pub(crate) impl_macro_name: Option<String>,
     pub(crate) container_type: ContainerType,
 }
 
@@ -103,10 +123,10 @@ pub fn parse_cli_args(args: &[String]) -> Result<CliArgs, CliParseError> {
         None => None,
     };
 
-    let guard_name = match args.iter().position(|s| *s == "--guard") {
+    let impl_macro_name = match args.iter().position(|s| *s == "--impl") {
         Some(idx) => match args.get(idx + 1) {
             Some(s) => Some(s),
-            None => return Err(CliParseError::MissingOperand("--guard")),
+            None => return Err(CliParseError::MissingOperand("--impl")),
         },
         None => None,
     };
@@ -217,7 +237,7 @@ pub fn parse_cli_args(args: &[String]) -> Result<CliArgs, CliParseError> {
         constness: constness,
         symbol_name: symbol_name.cloned(),
         namespace: namespace.cloned(),
-        guard_name: guard_name.cloned(),
+        impl_macro_name: impl_macro_name.cloned(),
         container_type: container_type,
     });
 }

src/constants.rs

@@ -28,8 +28,8 @@ OUTPUT OPTIONS:
 
 --symname NAME      Symbol name
 --namespace NAME    Namespace in which the symbol will exist    (C++ mode)
---guard NAME        Preprocessor macro to use for the header guard (#ifndef ...)
-                    (default: derive from output filename)
+--impl NAME         Preprocessor macro to use for the implementation guard
+                    in C mode   (default: derive from symbol name)
 
 CONTAINER TYPES:
 

src/generate.rs

@@ -1,16 +1,21 @@
 use std::fmt::Write;
 
+use thiserror::Error;
+
 use crate::{
-    HeaderGenerationError,
     cfg::Config,
     cli::{ByteType, Constness, ContainerType, Language},
 };
 
-pub fn with_header(
-    config: &Config,
-    in_data: &[u8],
-    buf: &mut String,
-) -> Result<(), HeaderGenerationError> {
+#[derive(Error, Debug)]
+pub enum HeaderGenerationError {
+    #[error("input file doesn't contain valid UTF-8: \"{0}\"")]
+    InvalidUtf8String(String),
+}
+
+pub fn header(config: &Config, in_data: &[u8]) -> Result<String, HeaderGenerationError> {
+    let mut buf = String::with_capacity(in_data.len() * 6);
+
     // Program banner at the top of the header file
     write!(
         buf,
@@ -22,24 +27,30 @@ pub fn with_header(
     .unwrap();
 
     // Header guard
+
     if config.language == Language::Cpp {
+        // C++ style
         write!(
             buf,
             "#if !defined({}){}",
-            config.guard_name, config.line_ending
+            config.header_guard, config.line_ending
         )
         .unwrap();
+        write!(buf, "#define {}{}", config.header_guard, config.line_ending).unwrap();
     } else {
-        write!(buf, "#ifndef {}{}", config.guard_name, config.line_ending).unwrap();
+        // C style
+        write!(buf, "#ifdef {}{}", config.impl_macro, config.line_ending).unwrap();
     }
-    write!(buf, "#define {}{}", config.guard_name, config.line_ending).unwrap();
 
-    with_includes(config, buf);
-    with_contents(config, in_data, buf)?;
+    // Includes & main content
+
+    with_contents(config, in_data, &mut buf)?;
+
+    // End header guard
 
     write!(buf, "#endif{}", config.line_ending).unwrap();
 
-    Ok(())
+    Ok(buf)
 }
 
 pub fn with_contents(
@@ -47,6 +58,21 @@ pub fn with_contents(
     in_data: &[u8],
     buf: &mut String,
 ) -> Result<(), HeaderGenerationError> {
+    with_includes(config, buf);
+
+    let length: usize = match config.container_type {
+        ContainerType::CString => in_data.len() + 1, // +1 for NUL terminator
+        _ => in_data.len(),
+    };
+
+    write!(
+        buf,
+        "{}{}",
+        length_define(config, length),
+        config.line_ending
+    )
+    .unwrap();
+
     if config.language == Language::Cpp {
         // C++ mode
 
@@ -61,9 +87,18 @@ pub fn with_contents(
         // C mode
 
         with_definition(config, in_data, buf)?;
+
         write!(buf, "#else{}", config.line_ending).unwrap();
+
         with_includes(config, buf);
-        with_declaration(config, in_data, buf);
+        write!(
+            buf,
+            "{}{}",
+            length_define(config, length),
+            config.line_ending
+        )
+        .unwrap();
+        with_declaration(config, buf);
     }
 
     Ok(())
@@ -78,15 +113,8 @@ pub fn with_includes(config: &Config, buf: &mut String) {
         "#include <stdint.h>"
     };
 
-    let stddef_h = if config.language == Language::Cpp {
-        "#include <cstddef>"
-    } else {
-        "#include <stddef.h>"
-    };
-
     match config.container_type {
         ContainerType::CArray(byte_type) => {
-            write!(buf, "{}{}", stddef_h, config.line_ending).unwrap();
             match byte_type {
                 ByteType::U8 => write!(buf, "{}{}", stdint_h, config.line_ending).unwrap(),
                 ByteType::I8 => write!(buf, "{}{}", stdint_h, config.line_ending).unwrap(),
@@ -102,15 +130,13 @@ pub fn with_includes(config: &Config, buf: &mut String) {
 
             write!(buf, "#include <array>{}", config.line_ending).unwrap();
         }
-        ContainerType::CString => {
-            write!(buf, "{}{}", stddef_h, config.line_ending).unwrap();
-        }
         ContainerType::StdString => {
             write!(buf, "#include <string>{}", config.line_ending).unwrap();
         }
         ContainerType::StdStringView => {
             write!(buf, "#include <string_view>{}", config.line_ending).unwrap();
         }
+        _ => (),
     };
 }
 
@@ -151,47 +177,16 @@ pub fn with_definition(
     in_data: &[u8],
     buf: &mut String,
 ) -> Result<(), HeaderGenerationError> {
-    let length: usize = match config.container_type {
-        ContainerType::CString => in_data.len() + 1,
-        _ => in_data.len(),
-    };
-
     let modifiers = definition_modifiers(config);
 
-    match config.container_type {
-        ContainerType::CArray(_) => {
-            write!(
-                buf,
-                "{}{} = {};{}",
-                modifiers,
-                length_data_type_symbol(config),
-                length,
-                config.line_ending
-            )
-            .unwrap();
-        }
-        ContainerType::CString => {
-            write!(
-                buf,
-                "{}{} = {};{}",
-                modifiers,
-                length_data_type_symbol(config),
-                length,
-                config.line_ending
-            )
-            .unwrap();
-        }
-        _ => (),
-    };
-
     write!(
         buf,
         "{}{} = {};{}",
         modifiers,
-        data_type_and_symbol(config, in_data),
+        data_type_and_symbol(config),
         match config.container_type {
-            ContainerType::CArray(_) => with_array_initialiser(in_data),
-            ContainerType::StdArray(_) => with_array_initialiser(in_data),
+            ContainerType::CArray(_) => with_array_initialiser(config, in_data),
+            ContainerType::StdArray(_) => with_array_initialiser(config, in_data),
             _ => with_string_initialiser(config, in_data)?,
         },
         config.line_ending
@@ -201,42 +196,47 @@ pub fn with_definition(
     Ok(())
 }
 
-pub fn with_declaration(config: &Config, in_data: &[u8], buf: &mut String) {
+pub fn with_declaration(config: &Config, buf: &mut String) {
     let modifiers = declaration_modifiers(config);
 
-    match config.container_type {
-        ContainerType::CArray(_) => {
-            write!(buf, "{}{};{}", modifiers, in_data.len(), config.line_ending).unwrap();
-        }
-        ContainerType::CString => {
-            write!(
-                buf,
-                "{}{};{}",
-                modifiers,
-                in_data.len() + 1,
-                config.line_ending
-            )
-            .unwrap();
-        }
-        _ => (),
-    };
-
     write!(
         buf,
         "{}{};{}",
         modifiers,
-        data_type_and_symbol(config, in_data),
+        data_type_and_symbol(config),
         config.line_ending
     )
     .unwrap();
 }
 
-pub fn with_array_initialiser(in_data: &[u8]) -> String {
+pub fn with_array_initialiser(config: &Config, in_data: &[u8]) -> String {
     let mut out_str: String = String::with_capacity(in_data.len() * 6 + 16);
 
+    let signed_literals = match config.container_type {
+        ContainerType::CArray(byte_type) => match byte_type {
+            ByteType::Char => true,
+            ByteType::I8 => true,
+            _ => false,
+        },
+        ContainerType::StdArray(byte_type) => match byte_type {
+            ByteType::Char => true,
+            ByteType::I8 => true,
+            _ => false,
+        },
+        _ => false,
+    };
+
     write!(out_str, "{{").unwrap();
-    for b in in_data {
-        write!(out_str, "{:#x},", b).unwrap();
+
+    if signed_literals {
+        for b in in_data {
+            let b = i8::from_ne_bytes([*b; 1]);
+            write!(out_str, "{},", b).unwrap();
+        }
+    } else {
+        for b in in_data {
+            write!(out_str, "{},", b).unwrap();
+        }
     }
     let _ = out_str.pop();
     write!(out_str, "}}").unwrap();
@@ -264,15 +264,10 @@ pub fn with_string_initialiser(
     Ok(out_str)
 }
 
-pub fn length_data_type_symbol(config: &Config) -> String {
+pub fn length_define(config: &Config, length: usize) -> String {
     let mut out_str = String::with_capacity(36 + config.symbol_name.len());
 
-    let size_type = match config.language {
-        Language::C => "size_t",
-        Language::Cpp => "std::size_t",
-    };
-
-    write!(out_str, "{} {}", size_type, length_symbol(config)).unwrap();
+    write!(out_str, "#define {} {}", length_symbol(config), length).unwrap();
 
     out_str
 }
@@ -280,60 +275,54 @@ pub fn length_data_type_symbol(config: &Config) -> String {
 pub fn length_symbol(config: &Config) -> String {
     let mut out_str = String::with_capacity(config.symbol_name.len() + 5);
 
-    write!(
-        out_str,
-        "{}{}",
-        config.symbol_name,
-        if config
-            .symbol_name
-            .chars()
-            .all(|c| c.is_uppercase() || c == '_')
-        {
-            "_LEN"
-        } else {
-            "_len"
-        },
-    )
-    .unwrap();
+    write!(out_str, "{}_LEN", config.symbol_name.to_uppercase(),).unwrap();
 
     out_str
 }
 
-pub fn data_type_and_symbol(config: &Config, in_data: &[u8]) -> String {
-    let u8_type = match config.language {
-        Language::C => "uint8_t",
-        Language::Cpp => "std::uint8_t",
-    };
-    let i8_type = match config.language {
-        Language::C => "int8_t",
-        Language::Cpp => "std::int8_t",
-    };
+pub fn data_type_and_symbol(config: &Config) -> String {
+    let mut out_str = String::with_capacity(config.symbol_name.len() + 20);
 
     let length_sym = length_symbol(config);
 
     match config.container_type {
-        ContainerType::CArray(byte_type) => match byte_type {
-            ByteType::UnsignedChar => {
-                format!("unsigned char {}[{}]", config.symbol_name, length_sym)
-            }
-            ByteType::Char => format!("char {}[{}]", config.symbol_name, length_sym),
-            _ => format!("{} {}[{}]", u8_type, config.symbol_name, length_sym),
-        },
-        ContainerType::StdArray(byte_type) => {
-            format!(
-                "std::array<{},{}> {}",
-                match byte_type {
-                    ByteType::UnsignedChar => "unsigned char",
-                    ByteType::Char => "char",
-                    ByteType::U8 => u8_type,
-                    ByteType::I8 => i8_type,
-                },
-                in_data.len(),
-                config.symbol_name
-            )
+        ContainerType::CArray(byte_type) => write!(
+            out_str,
+            "{} {}[{}]",
+            if config.language == Language::Cpp {
+                byte_type.to_cpp_type()
+            } else {
+                byte_type.to_c_type()
+            },
+            config.symbol_name,
+            length_sym
+        )
+        .unwrap(),
+        ContainerType::StdArray(byte_type) => write!(
+            out_str,
+            "std::array<{},{}> {}",
+            if config.language == Language::Cpp {
+                byte_type.to_cpp_type()
+            } else {
+                byte_type.to_c_type()
+            },
+            length_sym,
+            config.symbol_name
+        )
+        .unwrap(),
+        ContainerType::CString => write!(
+            out_str,
+            "{} {}[{}]",
+            ByteType::Char.to_c_type(),
+            config.symbol_name,
+            length_sym
+        )
+        .unwrap(),
+        ContainerType::StdString => write!(out_str, "std::string {}", config.symbol_name).unwrap(),
+        ContainerType::StdStringView => {
+            write!(out_str, "std::string_view {}", config.symbol_name).unwrap()
         }
-        ContainerType::CString => format!("char {}[{}]", config.symbol_name, length_sym),
-        ContainerType::StdString => format!("std::string {}", config.symbol_name),
-        ContainerType::StdStringView => format!("std::string_view {}", config.symbol_name),
-    }
+    };
+
+    out_str
 }

src/main.rs

@@ -1,10 +1,7 @@
-use std::io::{BufReader, BufWriter, Read, Write};
+use std::io::{self, BufReader, BufWriter, Read, Write};
+use std::path::Path;
 use std::{env, fs::OpenOptions, process::ExitCode};
 
-use thiserror::Error;
-
-use crate::cfg::Config;
-
 mod cfg;
 mod cli;
 mod constants;
@@ -43,10 +40,25 @@ fn main() -> ExitCode {
         }
     };
 
-    match write_header(&cfg) {
+    let in_data = match read_input_file(&cfg.input_file_path) {
+        Ok(v) => v,
+        Err(e) => {
+            eprintln!("Failed to read input file: {}", e);
+            return ExitCode::FAILURE;
+        }
+    };
+    let header_src = match generate::header(&cfg, &in_data) {
+        Ok(s) => s,
+        Err(e) => {
+            eprintln!("Failed to generate header source file: {}", e);
+            return ExitCode::FAILURE;
+        }
+    };
+
+    match write_output_file(header_src.as_bytes(), cfg.overwrite, &cfg.output_file_path) {
         Ok(_) => (),
         Err(e) => {
-            eprintln!("{}", e);
+            eprintln!("Failed to write output file: {}", e);
             return ExitCode::FAILURE;
         }
     };
@@ -54,48 +66,33 @@ fn main() -> ExitCode {
     return ExitCode::SUCCESS;
 }
 
-#[derive(Error, Debug)]
-pub enum HeaderGenerationError {
-    #[error("I/O error: \"{0}\"")]
-    IOError(String),
-    #[error("input file doesn't contain valid UTF-8: \"{0}\"")]
-    InvalidUtf8String(String),
-}
-
-fn write_header(config: &Config) -> Result<(), HeaderGenerationError> {
+fn read_input_file(input_path: &Path) -> Result<Vec<u8>, io::Error> {
     let in_file = OpenOptions::new()
         .read(true)
         .write(false)
-        .open(config.input_file_path.clone())
-        .expect("failed to open input file");
-
-    let mut buf = String::with_capacity(if let Ok(meta) = in_file.metadata() {
-        meta.len() as usize
-    } else {
-        0
-    });
+        .open(input_path)?;
 
+    let file_size = in_file.metadata()?.len();
+    let mut in_data: Vec<u8> = Vec::with_capacity(file_size as usize);
     let mut reader = BufReader::new(in_file);
-    let mut in_data: Vec<u8> = Vec::new();
-    let n_bytes_read = match reader.read_to_end(&mut in_data) {
-        Ok(n) => n,
-        Err(e) => return Err(HeaderGenerationError::IOError(e.to_string())),
-    };
 
-    generate::with_header(config, &in_data[..n_bytes_read], &mut buf)?;
+    let _ = reader.read_to_end(&mut in_data)?;
 
+    Ok(in_data)
+}
+
+fn write_output_file(buf: &[u8], overwrite: bool, output_path: &Path) -> Result<(), io::Error> {
+    if overwrite {
+        let _ = std::fs::remove_file(output_path);
+    }
     let out_file = OpenOptions::new()
         .write(true)
-        .truncate(config.overwrite)
-        .create(true)
-        .open(config.output_file_path.clone())
-        .expect("failed to open input file");
+        .create_new(true)
+        .open(output_path)?;
+
     let mut writer = BufWriter::new(out_file);
 
-    match writer.write_all(buf.as_bytes()) {
-        Ok(_) => (),
-        Err(e) => return Err(HeaderGenerationError::IOError(e.to_string())),
-    };
+    writer.write_all(buf)?;
 
     Ok(())
 }