Function process_files_parallel 

pub fn process_files_parallel<T, F, C, R>(
    files: &[String],
    processor: F,
    combiner: C,
) -> Result<(R, usize)>
where
    T: Send + 'static,
    R: Send + 'static,
    F: Fn(&str) -> Result<T> + Send + Sync,
    C: Fn(Vec<FileProcessResult<T>>) -> R + Send + Sync,

Process multiple files in parallel with memory-efficient streaming

This function processes files concurrently using a streaming approach that processes entries line-by-line without loading entire files into memory. This prevents memory allocation failures on large files.

Arguments

• files - List of file paths to process
• processor - Function that processes a single file with streaming callback
• combiner - Function that combines results from all files

Returns

Combined result from all files plus total lines processed