เทคนิคเกี่ยวกับลูปและ Calldata

Loops are dangerous for gas because every operation inside runs once per iteration. A single expensive call inside a loop can blow your gas budget or hit the block gas limit.

The goal is to push as much work as possible outside the loop and make each iteration as cheap as possible.

Reading array.length on a storage array costs an SLOAD each time the loop condition is checked. Cache the length in a local variable before the loop.

Never read or write the same storage slot repeatedly inside a loop. Accumulate into a local variable and write the result once after the loop ends.

Since Solidity 0.8, arithmetic has built-in overflow checks that cost extra gas. A loop counter that can never realistically overflow can be incremented inside an unchecked block.

++i is marginally cheaper than i++ because post-increment must produce a temporary copy of the old value. The saving is tiny per operation but adds up across many iterations.

Prefer ++i in loop counters where the return value is unused.

For external functions, declaring array and struct parameters as calldata instead of memory avoids copying the data into memory. Calldata is read-only and cheaper to access.

Each non-zero calldata byte costs 16 gas. Smaller payloads mean cheaper transactions. Techniques include:

• Packing multiple values into one uint256
• Using smaller types where the ABI allows
• Passing indices instead of full structs when the data is already on-chain

Logical operators && and || short-circuit: the second operand is only evaluated if needed. Order conditions so the cheapest or most-likely-decisive check comes first.

If you access the same calldata or memory element multiple times in a loop body, cache it in a local variable. While calldata access is cheaper than storage, repeated access still adds up.

Unbounded loops over user-controlled arrays can exceed the block gas limit, making the function permanently uncallable (a denial-of-service risk).

Always cap iteration counts or use a pull-based pattern where users process their own entries, keeping each transaction within safe gas bounds.

An optimized loop typically: caches the length, accumulates into locals, uses calldata inputs, increments with unchecked { ++i; }, and stays bounded.

Each trick is small alone, but combined they can cut loop gas by a large fraction.

You learned loop and calldata gas tricks:

• Cache array length before looping
• Accumulate in locals, write storage once
• Use unchecked { ++i; } for safe counters
• Prefer calldata parameters and shrink payloads
• Always bound loops to avoid gas-limit DoS

Next we measure these gains with profiling tools.