notreally.c

// this is pseudo-c

struct Pointers {
    const char *timestampStart;
    const char *timestampEnd;
    const char *pidStart;
    const char *pidEnd;
    const char *levelStart;
    const char *levelEnd;
    const char *prefixStart;
    const char *prefixEnd;
    const char *textStart;
    const char *textEnd;
};

#pragma pack(push, 1)
struct Header {
    time_t timestamp;
    char level[3];
    uint8_t prefixLen;
    uint16_t pid;
};
#pragma pack(pop)

bool
getPointers(const char *input, Pointers *into)
{
    into->timestampStart = input;
    into->timestampEnd = input + 15;
    into->pidStart = timestampEnd + 2;
    into->pidEnd = strchr(into->pidStart, ']');
    into->levelStart = into->pidEnd + 2;
    into->levelEnd = into->levelStart + 4;
    into->prefixStart = into->levelEnd + 1;
    into->prefixEnd = strchr(into->prefixStart + ' ');
    if (into->prefixEnd == nullptr) {
        return false;
    }
    into->textStart = strchr(into->prefixEnd, ': ');
    if (into->prefixStart == nullptr) {
        return false;
    }
    into->textEnd = strchr(into->textStart, '\n');
    return into->textEnd != nullptr;
}

void v1(const char *input, const Pointers *pointers)
{
    struct iovec vecs[5] {
        { into->timestampStart, into->timestampEnd - into->timestampStart },
        { into->pidStart, into->pidEnd - into->pidStart },
        { into->levelStart, into->levelEnd - into->levelStart },
        { into->prefixStart, into->prefixEnd - into->prefixStart },
        { into->textStart, into->textEnd - into->textStart },
    };
    ... writev(fd, vecs, 5);
}

void v2(const char *input, const Pointers * pointers)
{
    Header hdr;
    hdr.timestamp = parseTime(into->timestampStart, into->timestampEnd);
    memcpy(hdr.level, into->levelStart, 3);
    hdr.prefixLen = pointers->prefixEnd - pointers->prefixStart;
    hdr.pid = atoi(into->pidStart);
    struct iovec vecs[2] {
        { &hdr, sizeof(hdr) },
        { pointers->prefixStart, pointers->textEnd - pointers->prefixStart },
    };  
    ... writev(fd, vecs, 2);
}