account_resize

Overview

The account_resize syscall changes the data storage size of an account. This can be used to expand or shrink the account’s data capacity.

Syscall Code

Code: 0x07 (TN_SYSCALL_CODE_ACCOUNT_RESIZE)

C SDK Function

ulong tsys_account_resize(ulong account_idx, ulong new_size);

Arguments

account_idx · ulong · required

Index of the account to resize. Must be writable by the current program.

new_size · ulong · required

New data size for the account in bytes. Must not exceed maximum account data size.

Return Value

Returns a syscall result code:

Success · ulong

• TN_VM_SYSCALL_SUCCESS (0) - Account resized successfully

Error Codes · ulong

• TN_VM_ERR_SYSCALL_INVALID_ACCOUNT_INDEX (-8) - Account index out of bounds
• TN_VM_ERR_SYSCALL_ACCOUNT_DOES_NOT_EXIST (-9) - Account does not exist
• TN_VM_ERR_SYSCALL_ACCOUNT_NOT_WRITABLE (-10) - Account not writable by current program
• TN_VM_ERR_SYSCALL_ACCOUNT_TOO_BIG (-12) - New size exceeds maximum allowed
• TN_VM_ERR_SYSCALL_INSUFFICIENT_PAGES (-26) - Not enough pages available for expansion

Resource Consumption

Compute Units

• Base cost: TN_VM_SYSCALL_BASE_COST (512 units)
• Additional cost: None (size changes don’t directly affect compute cost)
• Total cost: Fixed at 512 units regardless of new size

Memory Pages

• Page allocation: New pages allocated from transaction pool when expanding
• Page deallocation: Excess pages returned to transaction pool when shrinking
• Page granularity: Account data is managed in page-sized chunks
• Minimum allocation: Account metadata always requires at least one page

Side Effects

• Data size: Changes the account’s data size to the specified value
• Memory allocation: Allocates or frees pages as needed
• Metadata: Makes account metadata and data writable if not already
• Data preservation: Existing data is preserved when expanding

Usage Notes

• The new size must not exceed TN_ACCOUNT_DATA_SZ_MAX
• When expanding: additional space is allocated and initialized
• When shrinking: excess data is truncated and pages may be freed
• If new size equals current size, the syscall succeeds immediately
• Account must be writable by the current program
• Sufficient pages must be available in the transaction’s page pool

Memory Management

• Expansion: Allocates additional pages from the transaction page pool
• Shrinking: May free pages back to the pool (implementation dependent)
• Page alignment: Account data is managed in page-sized chunks
• Data preservation: Existing data within the new size is preserved

Example

#include <thru-sdk/c/tn_sdk_syscall.h>

// Resize account data to 2048 bytes
ulong account_idx = 1;
ulong new_size = 2048;

ulong result = tsys_account_resize(account_idx, new_size);

if (result == TN_VM_SYSCALL_SUCCESS) {
    // Account data size changed to 2048 bytes
    // Existing data preserved (up to new size)
    // Additional space initialized if expanded
}

// Check current size without changing it
result = tsys_account_resize(account_idx, current_size);
// This will succeed immediately if current_size matches actual size