swap_handle_get_printable_amount()

ledger-secure-sdk/lib_standard_app/swap_entrypoints.h

/* This handle is called when the Exchange application wants to format for
 * display an amount + ticker of a currency known by this application
 *
 * If the formatting succeeds, result is set to the formatted string. Otherwise
 * it is set to '\0'.
 */
void swap_handle_get_printable_amount(get_printable_amount_parameters_t *params);

ledger-secure-sdk/lib_standard_app/swap_lib_calls.h

typedef struct get_printable_amount_parameters_s {
    // INPUTS //
    // Additional data when dealing with tokens
    // Content is coin application specific
    uint8_t *coin_configuration;
    uint8_t  coin_configuration_length;

    // Raw amount in big number format
    uint8_t *amount;
    uint8_t  amount_length;

    // Set to true if the amount to format is the fee of the swap.
    bool is_fee;

    // OUTPUT //
    // Set to the formatted string if the formatting succeeds. 0 otherwise.
    char printable_amount[MAX_PRINTABLE_AMOUNT_SIZE];
} get_printable_amount_parameters_t;

---

Example of handle implementation in Boilerplate

app-boilerplate/src/swap/handle_get_printable_amount.c

#ifdef HAVE_SWAP
#include "swap.h"
#include "buffer.h"
#include "constants.h"
#include "format.h"
#include "os.h"

#include <string.h>
#include <stdio.h>

/* Format printable amount including the ticker from specified parameters.
 *
 * Must set empty printable_amount on error, printable amount otherwise
 * get_printable_amount_parameters_t is defined in C SDK as:
 * struct {
 *   // IN
 *   uint8_t *coin_configuration;
 *   uint8_t  coin_configuration_length;
 *   uint8_t *amount;
 *   uint8_t  amount_length;
 *   bool     is_fee;
 *   // OUT
 *   char printable_amount[MAX_PRINTABLE_AMOUNT_SIZE];
 * } get_printable_amount_parameters_t;
 */
void swap_handle_get_printable_amount(get_printable_amount_parameters_t* params) {
    PRINTF("Inside swap_handle_get_printable_amount\n");

    PRINTF("Amount: %.*H\n", params->amount_length, params->amount);

    char amount[30] = {0};
    memset(params->printable_amount, 0, sizeof(params->printable_amount));

    /// Convert params->amount into uint64_t
    uint64_t value = 0;
    if (swap_str_to_u64(params->amount, params->amount_length, &value)) {
        format_fpu64(amount, sizeof(amount), value, EXPONENT_SMALLEST_UNIT);
        PRINTF("Formatted amount: %s\n", amount);
        snprintf(params->printable_amount,
                 sizeof(params->printable_amount),
                 "BOL %.*s",
                 sizeof(amount),
                 amount);
    } else {
        PRINTF("Failed to convert amount to uint64_t\n");
    }
}
#endif  // HAVE_SWAP