struct ara::log::Format

Structure ara::log::Format serves as a formatting hint in the logging system and bundles format specifier fmt ([SWS_LOG_00225]) with precision specification precision ([SWS_LOG_00226]). Instances should preferably be created via provided helper functions, with the evaluation of precision distinguishing between minimum number of digits for integers and decimal places for floating-point numbers depending on the format type. For integer types, a precision of zero is treated like one, while the field is completely ignored under Fmt::kDefault.

more ›

Context

Data structure ara::log::Format serves in the logging framework of the AUTOSAR Adaptive Platform as a formatting hint for outputting formatted values. For this purpose, it bundles two central properties: format specification fmt of enumeration type Fmt ([SWS_LOG_00225]) and the associated precision precision as std::uint16_t ([SWS_LOG_00226]). Interaction partners are output components and formatting streams of the logging module as well as the application logic that creates log messages with formatted text output. Interpretation: The helper functions mentioned in the specification for instantiation are likely located directly in module ara::log to provide standardized formatters. Question Q-1c465e69c99359fa (open)

Lifecycle

As a final data structure (struct Format final), ara::log::Format has no internal state machine and no complex phase transitions. Although the attributes are declared as public variables ([SWS_LOG_00225], [SWS_LOG_00226]), the specification explicitly requires not creating instances manually, but instead using the provided helper functions. Instances are typically short-lived value objects that are passed to log streams by copy or by reference. Interpretation: Since the structure exhibits no internal synchronization, copies and concurrent read accesses across thread boundaries are likely thread-safe, whereas mutating accesses must be synchronized externally. Question Q-bd0f1147e9472c19 (open)

Usage Path

Typical usage includes defining the format specifier fmt ([SWS_LOG_00225]) and specifying the desired precision precision ([SWS_LOG_00226]). The evaluation of precision depends on the selected type in fmt:

• Integer types: For Fmt::kDec, Fmt::kOct, Fmt::kHex, and Fmt::kBin, precision designates the minimum number of digits to be output, analogous to formatting via std::printf("%.7d").
• Floating-point types with fixed-point and exponential representation: For Fmt::kDecFloat, Fmt::kEngFloat, and Fmt::kHexFloat, precision specifies the exact number of decimal places.
• Automatic floating-point representation: Under Fmt::kAutoFloat, precision defines the number of significant digits according to the rules of the format specifier %g in std::printf.
• Default formatting: If fmt holds the value Fmt::kDefault, the specification in precision is ignored and implementation-defined formatting is applied.

Activity diagram: Branching logic for evaluating precision depending on fmt. Sources: [SWS_LOG_00225], [SWS_LOG_00226]

Error Scenarios

The structure does not define any error codes or exceptions; edge cases are instead handled fault-tolerantly and deterministically. For integer format specifiers (Fmt::kDec, Fmt::kOct, Fmt::kHex, Fmt::kBin), a value of precision = 0 ([SWS_LOG_00226]) is evaluated semantically identically to a value of 1 to prevent blank outputs. If fmt is set to Fmt::kDefault ([SWS_LOG_00225]), a set value in precision does not lead to an error state, but is silently discarded.