from SEGGER.h:150
typedef struct
{
void (*pfStoreChar) (SEGGER_BUFFER_DESC* pBufferDesc, SEGGER_SNPRINTF_CONTEXT* pContext, char c);
int (*pfPrintUnsigned) (SEGGER_BUFFER_DESC* pBufferDesc, SEGGER_SNPRINTF_CONTEXT* pContext, U32 v, unsigned Base, char Flags, int Width, int Precision);
int (*pfPrintInt) (SEGGER_BUFFER_DESC* pBufferDesc, SEGGER_SNPRINTF_CONTEXT* pContext, I32 v, unsigned Base, char Flags, int Width, int Precision);
} SEGGER_PRINTF_API;