1,000+ ASIC Interview Questions: SystemVerilog, UVM & RTL

DescriptionQ534

Q534FWASIC interview problem

Measure the final UART command token

TechniquesFWBufferBackward scanBoundsUART

DifficultyEasy

TopicFirmware Algorithms

LanguageSystemVerilog

Requirements4 checkpoints

Problem

Measure the last token in an explicitly sized UART command buffer after ignoring trailing ASCII space bytes.

Type declarationSystemVerilog

typedef enum { TOKEN_OK, TOKEN_EINVAL } token_rc_t;
token_rc_t last_token_len(const uint8_t *buf,
                          size_t len,
                          size_t *token_len);
// len <= 128; only 0x20 separates tokens.

Example input and output

Use this case to check your interpretation

Input

buffer bytes="run test   ", explicit_length=11

Output

last_token_length=4 ("test")

Explanation

Trailing ASCII spaces are skipped, then the scan stops at the separator before test without relying on a terminator.

Requirements (4)

Treat only byte 0x20 as a separator; embedded zero and nonprinting bytes remain token data.
Return zero for an empty or all-space input.
Scan with unsigned indexes without decrementing below zero, calling strlen, allocating, or mutating the buffer.
Reject a null output, length above 128, or null nonempty input without changing the caller's old length.