import t, c
from stdint import *


class Buf:
    data: char*
    length: sizet
    capacity: sizet
    owned: bool

    def __init__(self, data: char*, capacity: sizet, length: sizet = 0, owned: bool = False):
        self.data = data
        self.capacity = capacity
        self.length = length
        self.owned = owned

    def clear(self):
        self.length = 0
        if self.data != None and self.capacity > 0: self.data[0] = 0

    def write(self, src: char*, count: sizet) -> sizet:
        if self.data == None: return 0
        if src == None: return 0
        if count == 0: return 0
        avail: sizet = self.capacity - self.length
        if avail <= 0: return 0
        n: sizet = count if count < avail else avail
        for i in range(n):
            self.data[self.length + i] = src[i]
        self.length += n
        # When exactly full (n==avail), data[capacity] would overflow by 1 byte, so guard it
        if self.length < self.capacity: self.data[self.length] = 0
        return n

    def cstr(self) -> char*:
        return self.data

    def reset(self):
        self.length = 0
        if self.data != None and self.capacity > 0:
            self.data[0] = 0

    def __enter__(self) -> Buf*: return self
    def __exit__(self): self.reset()

    def free(self):
        if self.owned and self.data != None:
            self.data[0] = 0
            self.owned = False
        self.data = None
        self.length = 0
        self.capacity = 0