Documentation improvements

#include "android-base/logging.h"

// The name of the file containing the distro version information.

// See also libcore.tzdata.update2.TimeZoneDistro / libcore.tzdata.update2.DistroVersion.

static const char* DISTRO_VERSION_FILENAME = "/distro_version";

// distro_version is an ASCII file consisting of 17 bytes in the form: AAA.BBB|CCCCC|DDD

// AAA.BBB is the major/minor version of the distro format (e.g. 001.001),

// CCCCC is the rules version (e.g. 2016g)

// DDD is the android revision for this rules version to allow for distro corrections (e.g. 001)

// We only need the first 13 to determine if it is suitable for the device.

static const int DISTRO_VERSION_LENGTH = 13;

// The major version of the distro format supported by this code as a null-terminated char[].

// See also libcore.tzdata.update2.TimeZoneDistro / libcore.tzdata.update2.DistroVersion.

static const char SUPPORTED_DISTRO_MAJOR_VERSION[] = "001";

// The length of the distro format major version excluding the \0

static const size_t SUPPORTED_DISTRO_MAJOR_VERSION_LEN = sizeof(SUPPORTED_DISTRO_MAJOR_VERSION) - 1;

// The minor version of the distro format supported by this code as a null-terminated char[].

// See also libcore.tzdata.update2.TimeZoneDistro / libcore.tzdata.update2.DistroVersion.

static const char SUPPORTED_DISTRO_MINOR_VERSION[] = "001";

// The length of the distro format minor version excluding the \0

static const size_t SUPPORTED_DISTRO_MINOR_VERSION_LEN = sizeof(SUPPORTED_DISTRO_MINOR_VERSION) - 1;

// The length of the distro format version. e.g. 001.001

static const size_t SUPPORTED_DISTRO_VERSION_LEN =

        SUPPORTED_DISTRO_MAJOR_VERSION_LEN + SUPPORTED_DISTRO_MINOR_VERSION_LEN + 1;

// The length of the IANA rules version bytes. e.g. 2016a

static const size_t RULES_VERSION_LEN = 5;

// Distro version bytes are: AAA.BBB|CCCCC - the rules version is CCCCC

static const size_t DISTRO_VERSION_RULES_IDX = 8;

// See also libcore.tzdata.update2.TimeZoneDistro.

static const char* TZDATA_FILENAME = "/tzdata";

// tzdata file header (as much as we need for the version):

// byte[11] tzdata_version  -- e.g. "tzdata2012f"

static const int TZ_HEADER_LENGTH = 11;

// The major version of the distro format supported by this code as a null-terminated char[].

static const char TZ_DATA_HEADER_PREFIX[] = "tzdata";

static const size_t TZ_DATA_HEADER_PREFIX_LEN = sizeof(TZ_DATA_HEADER_PREFIX) - 1; // exclude \0