Custom Text File Data Reading Function with Multiple Read Modes

The following demonstrates a custom function for reading text file data with the following capabilities: - Read entire file contents - Read specific line N using direct line indexing - Read lines from M to N through line range extraction - Read from line M to the Nth line from the end using negative indexing - Read data starting from (or ending at) the M-th occurrence of string str (supports last occurrence or M-th from last) through pattern matching and occurrence counting This function enables flexible text file operations, particularly useful when processing large files where only specific lines or data segments need to be accessed, significantly improving processing efficiency. The implementation uses line-by-line reading with conditional logic to handle different read modes while optimizing memory usage. The function can be extended based on user requirements, such as adding support for specific character encodings through encoding parameters, or incorporating write operations to modify text files. The core algorithm involves file stream handling, line counter management, and string search operations with configurable start/end positions. Key implementation aspects include: - Using file pointer manipulation for efficient large file handling - Implementing occurrence counting through iterative string matching - Supporting both positive and negative line indexing with boundary checks - Providing option flags for reading from start or end of matched lines This function aims to provide comprehensive text processing solutions and hopes to benefit users in their data handling tasks.