Mapping vs Array Storage Cost Comparator

WHAT IT DOES

The Mapping vs Array Storage Cost Comparator is a developer tool that analyzes Solidity source code to compare the storage efficiency of mappings versus arrays. It parses contract source to identify all state variables, with special focus on mapping declarations and array definitions. The tool calculates estimated gas costs per storage slot, per entry, and provides side-by-side comparisons of different storage patterns. This helps developers make informed decisions about data structure choices during contract design.

HOW TO USE

Paste your Solidity contract source code into the analyzer. The tool processes the code, extracting all mapping and array declarations along with regular state variables. It displays detailed breakdowns showing each variable's storage footprint, estimated gas costs, and structural characteristics. Results are presented in clear tables with mappings grouped separately from arrays, making it easy to compare costs at a glance. The analysis includes key insights about which structure appears more efficient for your specific use case.

TECHNICAL MECHANISM

The analyzer operates through static parsing of Solidity source code. It first strips comments and string literals to avoid false positives, then scans for mapping and array declarations using regex patterns. The tool detects struct definitions and correctly handles nested types, calculating the number of storage slots each variable consumes. For mappings, it calculates the cost per entry as the sum of key slot and value slot(s) - each requiring approximately 20,000 gas for SSTORE operations. For arrays, it distinguishes between fixed-size and dynamic arrays, accounting for the additional length slot in dynamic arrays. Struct field expansion is handled recursively, with each field occupying one or more storage slots depending on EVM packing rules. The tool provides comparative analysis by averaging costs across all variables of each type, helping developers identify which data structure offers better gas efficiency for their specific contract architecture.

WHAT IT CANNOT SEE

The tool cannot determine actual gas costs without executing the contract, as runtime conditions significantly affect storage costs. It cannot account for variable gas prices or EIP-2929 access costs that change based on whether storage slots have been accessed before. The tool cannot predict dynamic array growth patterns, which affect long-term storage costs. It cannot analyze storage optimizations across multiple contracts or detect storage collisions that depend on runtime logic. The tool cannot identify storage overwrites that occur conditionally, nor can it account for storage packing optimizations that the Solidity compiler might apply. It does not analyze access patterns or frequency, which dramatically impact overall gas usage. The tool cannot validate whether mappings or arrays are actually used efficiently in practice.

PLEASE NOTE

This tool is designed for Ethereum Virtual Machine (EVM) compatible chains only. All gas estimations are approximations based on standard SSTORE/SLOAD costs and should be validated through testnet deployment. The analysis provides valuable insights for contract optimization but should not replace actual gas profiling. For critical applications, always verify storage costs through transaction execution on your target network. The tool assumes standard Solidity storage layout and may not account for custom compiler optimizations or non-standard storage patterns.