thodg/libgit2/src/buffer.c

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• Hash : d0656ac8
  Author :
  Date : 2020-06-27T12:15:26
  

  Make the tests run cleanly under UndefinedBehaviorSanitizer This change makes the tests run cleanly under `-fsanitize=undefined,nullability` and comprises of: * Avoids some arithmetic with NULL pointers (which UBSan does not like). * Avoids an overflow in a shift, due to an uint8_t being implicitly converted to a signed 32-bit signed integer after being shifted by a 32-bit signed integer. * Avoids a unaligned read in libgit2. * Ignores unaligned reads in the SHA1 library, since it only happens on Intel processors, where it is _still_ undefined behavior, but the semantics are moderately well-understood. Of notable omission is `-fsanitize=integer`, since there are lots of warnings in zlib and the SHA1 library which probably don't make sense to fix and I could not figure out how to silence easily. libgit2 itself also has ~100s of warnings which are mostly innocuous (e.g. use of enum constants that only fit on an `uint32_t`, but there is no way to do that in a simple fashion because the data type chosen for enumerated types is implementation-defined), and investigating whether there are worrying warnings would need reducing the noise significantly.

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• src/buffer.c

• /*
   * Copyright (C) the libgit2 contributors. All rights reserved.
   *
   * This file is part of libgit2, distributed under the GNU GPL v2 with
   * a Linking Exception. For full terms see the included COPYING file.
   */
  #include "buffer.h"
  #include "posix.h"
  #include "git2/buffer.h"
  #include "buf_text.h"
  #include <ctype.h>
  
  /* Used as default value for git_buf->ptr so that people can always
   * assume ptr is non-NULL and zero terminated even for new git_bufs.
   */
  char git_buf__initbuf[1];
  
  char git_buf__oom[1];
  
  #define ENSURE_SIZE(b, d) \
  	if ((b)->ptr == git_buf__oom || \
  	    ((d) > (b)->asize && git_buf_grow((b), (d)) < 0))\
  		return -1;
  
  
  int git_buf_init(git_buf *buf, size_t initial_size)
  {
  	buf->asize = 0;
  	buf->size = 0;
  	buf->ptr = git_buf__initbuf;
  
  	ENSURE_SIZE(buf, initial_size);
  
  	return 0;
  }
  
  int git_buf_try_grow(
  	git_buf *buf, size_t target_size, bool mark_oom)
  {
  	char *new_ptr;
  	size_t new_size;
  
  	if (buf->ptr == git_buf__oom)
  		return -1;
  
  	if (buf->asize == 0 && buf->size != 0) {
  		git_error_set(GIT_ERROR_INVALID, "cannot grow a borrowed buffer");
  		return GIT_EINVALID;
  	}
  
  	if (!target_size)
  		target_size = buf->size;
  
  	if (target_size <= buf->asize)
  		return 0;
  
  	if (buf->asize == 0) {
  		new_size = target_size;
  		new_ptr = NULL;
  	} else {
  		new_size = buf->asize;
  		/*
  		 * Grow the allocated buffer by 1.5 to allow
  		 * re-use of memory holes resulting from the
  		 * realloc. If this is still too small, then just
  		 * use the target size.
  		 */
  		if ((new_size = (new_size << 1) - (new_size >> 1)) < target_size)
  			new_size = target_size;
  		new_ptr = buf->ptr;
  	}
  
  	/* round allocation up to multiple of 8 */
  	new_size = (new_size + 7) & ~7;
  
  	if (new_size < buf->size) {
  		if (mark_oom) {
  			if (buf->ptr && buf->ptr != git_buf__initbuf)
  				git__free(buf->ptr);
  			buf->ptr = git_buf__oom;
  		}
  
  		git_error_set_oom();
  		return -1;
  	}
  
  	new_ptr = git__realloc(new_ptr, new_size);
  
  	if (!new_ptr) {
  		if (mark_oom) {
  			if (buf->ptr && (buf->ptr != git_buf__initbuf))
  				git__free(buf->ptr);
  			buf->ptr = git_buf__oom;
  		}
  		return -1;
  	}
  
  	buf->asize = new_size;
  	buf->ptr   = new_ptr;
  
  	/* truncate the existing buffer size if necessary */
  	if (buf->size >= buf->asize)
  		buf->size = buf->asize - 1;
  	buf->ptr[buf->size] = '\0';
  
  	return 0;
  }
  
  int git_buf_grow(git_buf *buffer, size_t target_size)
  {
  	return git_buf_try_grow(buffer, target_size, true);
  }
  
  int git_buf_grow_by(git_buf *buffer, size_t additional_size)
  {
  	size_t newsize;
  
  	if (GIT_ADD_SIZET_OVERFLOW(&newsize, buffer->size, additional_size)) {
  		buffer->ptr = git_buf__oom;
  		return -1;
  	}
  
  	return git_buf_try_grow(buffer, newsize, true);
  }
  
  void git_buf_dispose(git_buf *buf)
  {
  	if (!buf) return;
  
  	if (buf->asize > 0 && buf->ptr != NULL && buf->ptr != git_buf__oom)
  		git__free(buf->ptr);
  
  	git_buf_init(buf, 0);
  }
  
  #ifndef GIT_DEPRECATE_HARD
  void git_buf_free(git_buf *buf)
  {
  	git_buf_dispose(buf);
  }
  #endif
  
  void git_buf_sanitize(git_buf *buf)
  {
  	if (buf->ptr == NULL) {
  		assert(buf->size == 0 && buf->asize == 0);
  		buf->ptr = git_buf__initbuf;
  	} else if (buf->asize > buf->size)
  		buf->ptr[buf->size] = '\0';
  }
  
  void git_buf_clear(git_buf *buf)
  {
  	buf->size = 0;
  
  	if (!buf->ptr) {
  		buf->ptr = git_buf__initbuf;
  		buf->asize = 0;
  	}
  
  	if (buf->asize > 0)
  		buf->ptr[0] = '\0';
  }
  
  int git_buf_set(git_buf *buf, const void *data, size_t len)
  {
  	size_t alloclen;
  
  	if (len == 0 || data == NULL) {
  		git_buf_clear(buf);
  	} else {
  		if (data != buf->ptr) {
  			GIT_ERROR_CHECK_ALLOC_ADD(&alloclen, len, 1);
  			ENSURE_SIZE(buf, alloclen);
  			memmove(buf->ptr, data, len);
  		}
  
  		buf->size = len;
  		if (buf->asize > buf->size)
  			buf->ptr[buf->size] = '\0';
  
  	}
  	return 0;
  }
  
  int git_buf_is_binary(const git_buf *buf)
  {
  	return git_buf_text_is_binary(buf);
  }
  
  int git_buf_contains_nul(const git_buf *buf)
  {
  	return git_buf_text_contains_nul(buf);
  }
  
  int git_buf_sets(git_buf *buf, const char *string)
  {
  	return git_buf_set(buf, string, string ? strlen(string) : 0);
  }
  
  int git_buf_putc(git_buf *buf, char c)
  {
  	size_t new_size;
  	GIT_ERROR_CHECK_ALLOC_ADD(&new_size, buf->size, 2);
  	ENSURE_SIZE(buf, new_size);
  	buf->ptr[buf->size++] = c;
  	buf->ptr[buf->size] = '\0';
  	return 0;
  }
  
  int git_buf_putcn(git_buf *buf, char c, size_t len)
  {
  	size_t new_size;
  	GIT_ERROR_CHECK_ALLOC_ADD(&new_size, buf->size, len);
  	GIT_ERROR_CHECK_ALLOC_ADD(&new_size, new_size, 1);
  	ENSURE_SIZE(buf, new_size);
  	memset(buf->ptr + buf->size, c, len);
  	buf->size += len;
  	buf->ptr[buf->size] = '\0';
  	return 0;
  }
  
  int git_buf_put(git_buf *buf, const char *data, size_t len)
  {
  	if (len) {
  		size_t new_size;
  
  		assert(data);
  
  		GIT_ERROR_CHECK_ALLOC_ADD(&new_size, buf->size, len);
  		GIT_ERROR_CHECK_ALLOC_ADD(&new_size, new_size, 1);
  		ENSURE_SIZE(buf, new_size);
  		memmove(buf->ptr + buf->size, data, len);
  		buf->size += len;
  		buf->ptr[buf->size] = '\0';
  	}
  	return 0;
  }
  
  int git_buf_puts(git_buf *buf, const char *string)
  {
  	assert(string);
  	return git_buf_put(buf, string, strlen(string));
  }
  
  static const char base64_encode[] =
  	"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
  
  int git_buf_encode_base64(git_buf *buf, const char *data, size_t len)
  {
  	size_t extra = len % 3;
  	uint8_t *write, a, b, c;
  	const uint8_t *read = (const uint8_t *)data;
  	size_t blocks = (len / 3) + !!extra, alloclen;
  
  	GIT_ERROR_CHECK_ALLOC_ADD(&blocks, blocks, 1);
  	GIT_ERROR_CHECK_ALLOC_MULTIPLY(&alloclen, blocks, 4);
  	GIT_ERROR_CHECK_ALLOC_ADD(&alloclen, alloclen, buf->size);
  
  	ENSURE_SIZE(buf, alloclen);
  	write = (uint8_t *)&buf->ptr[buf->size];
  
  	/* convert each run of 3 bytes into 4 output bytes */
  	for (len -= extra; len > 0; len -= 3) {
  		a = *read++;
  		b = *read++;
  		c = *read++;
  
  		*write++ = base64_encode[a >> 2];
  		*write++ = base64_encode[(a & 0x03) << 4 | b >> 4];
  		*write++ = base64_encode[(b & 0x0f) << 2 | c >> 6];
  		*write++ = base64_encode[c & 0x3f];
  	}
  
  	if (extra > 0) {
  		a = *read++;
  		b = (extra > 1) ? *read++ : 0;
  
  		*write++ = base64_encode[a >> 2];
  		*write++ = base64_encode[(a & 0x03) << 4 | b >> 4];
  		*write++ = (extra > 1) ? base64_encode[(b & 0x0f) << 2] : '=';
  		*write++ = '=';
  	}
  
  	buf->size = ((char *)write) - buf->ptr;
  	buf->ptr[buf->size] = '\0';
  
  	return 0;
  }
  
  /* The inverse of base64_encode */
  static const int8_t base64_decode[] = {
  	-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
  	-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
  	-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 62, -1, -1, -1, 63,
  	52, 53, 54, 55, 56, 57, 58, 59, 60, 61, -1, -1, -1,  0, -1, -1,
  	-1,  0,  1,  2,  3,  4,  5,  6,  7,  8,  9, 10, 11, 12, 13, 14,
  	15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, -1, -1, -1, -1, -1,
  	-1, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40,
  	41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, -1, -1, -1, -1, -1,
  	-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
  	-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
  	-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
  	-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
  	-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
  	-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
  	-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
  	-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1
  };
  
  int git_buf_decode_base64(git_buf *buf, const char *base64, size_t len)
  {
  	size_t i;
  	int8_t a, b, c, d;
  	size_t orig_size = buf->size, new_size;
  
  	if (len % 4) {
  		git_error_set(GIT_ERROR_INVALID, "invalid base64 input");
  		return -1;
  	}
  
  	assert(len % 4 == 0);
  	GIT_ERROR_CHECK_ALLOC_ADD(&new_size, (len / 4 * 3), buf->size);
  	GIT_ERROR_CHECK_ALLOC_ADD(&new_size, new_size, 1);
  	ENSURE_SIZE(buf, new_size);
  
  	for (i = 0; i < len; i += 4) {
  		if ((a = base64_decode[(unsigned char)base64[i]]) < 0 ||
  			(b = base64_decode[(unsigned char)base64[i+1]]) < 0 ||
  			(c = base64_decode[(unsigned char)base64[i+2]]) < 0 ||
  			(d = base64_decode[(unsigned char)base64[i+3]]) < 0) {
  			buf->size = orig_size;
  			buf->ptr[buf->size] = '\0';
  
  			git_error_set(GIT_ERROR_INVALID, "invalid base64 input");
  			return -1;
  		}
  
  		buf->ptr[buf->size++] = ((a << 2) | (b & 0x30) >> 4);
  		buf->ptr[buf->size++] = ((b & 0x0f) << 4) | ((c & 0x3c) >> 2);
  		buf->ptr[buf->size++] = (c & 0x03) << 6 | (d & 0x3f);
  	}
  
  	buf->ptr[buf->size] = '\0';
  	return 0;
  }
  
  static const char base85_encode[] =
  	"0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz!#$%&()*+-;<=>?@^_`{|}~";
  
  int git_buf_encode_base85(git_buf *buf, const char *data, size_t len)
  {
  	size_t blocks = (len / 4) + !!(len % 4), alloclen;
  
  	GIT_ERROR_CHECK_ALLOC_MULTIPLY(&alloclen, blocks, 5);
  	GIT_ERROR_CHECK_ALLOC_ADD(&alloclen, alloclen, buf->size);
  	GIT_ERROR_CHECK_ALLOC_ADD(&alloclen, alloclen, 1);
  
  	ENSURE_SIZE(buf, alloclen);
  
  	while (len) {
  		uint32_t acc = 0;
  		char b85[5];
  		int i;
  
  		for (i = 24; i >= 0; i -= 8) {
  			uint8_t ch = *data++;
  			acc |= (uint32_t)ch << i;
  
  			if (--len == 0)
  				break;
  		}
  
  		for (i = 4; i >= 0; i--) {
  			int val = acc % 85;
  			acc /= 85;
  
  			b85[i] = base85_encode[val];
  		}
  
  		for (i = 0; i < 5; i++)
  			buf->ptr[buf->size++] = b85[i];
  	}
  
  	buf->ptr[buf->size] = '\0';
  
  	return 0;
  }
  
  /* The inverse of base85_encode */
  static const int8_t base85_decode[] = {
  	-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
  	-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
  	-1, 63, -1, 64, 65, 66, 67, -1, 68, 69, 70, 71, -1, 72, -1, -1,
  	 1,  2,  3,  4,  5,  6,  7,  8,  9, 10, -1, 73, 74, 75, 76, 77,
  	78, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25,
  	26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, -1, -1, -1, 79, 80,
  	81, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51,
  	52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 82, 83, 84, 85, -1,
  	-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
  	-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
  	-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
  	-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
  	-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
  	-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
  	-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
  	-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1
  };
  
  int git_buf_decode_base85(
  	git_buf *buf,
  	const char *base85,
  	size_t base85_len,
  	size_t output_len)
  {
  	size_t orig_size = buf->size, new_size;
  
  	if (base85_len % 5 ||
  		output_len > base85_len * 4 / 5) {
  		git_error_set(GIT_ERROR_INVALID, "invalid base85 input");
  		return -1;
  	}
  
  	GIT_ERROR_CHECK_ALLOC_ADD(&new_size, output_len, buf->size);
  	GIT_ERROR_CHECK_ALLOC_ADD(&new_size, new_size, 1);
  	ENSURE_SIZE(buf, new_size);
  
  	while (output_len) {
  		unsigned acc = 0;
  		int de, cnt = 4;
  		unsigned char ch;
  		do {
  			ch = *base85++;
  			de = base85_decode[ch];
  			if (--de < 0)
  				goto on_error;
  
  			acc = acc * 85 + de;
  		} while (--cnt);
  		ch = *base85++;
  		de = base85_decode[ch];
  		if (--de < 0)
  			goto on_error;
  
  		/* Detect overflow. */
  		if (0xffffffff / 85 < acc ||
  			0xffffffff - de < (acc *= 85))
  			goto on_error;
  
  		acc += de;
  
  		cnt = (output_len < 4) ? (int)output_len : 4;
  		output_len -= cnt;
  		do {
  			acc = (acc << 8) | (acc >> 24);
  			buf->ptr[buf->size++] = acc;
  		} while (--cnt);
  	}
  
  	buf->ptr[buf->size] = 0;
  
  	return 0;
  
  on_error:
  	buf->size = orig_size;
  	buf->ptr[buf->size] = '\0';
  
  	git_error_set(GIT_ERROR_INVALID, "invalid base85 input");
  	return -1;
  }
  
  #define HEX_DECODE(c) ((c | 32) % 39 - 9)
  
  int git_buf_decode_percent(
  	git_buf *buf,
  	const char *str,
  	size_t str_len)
  {
  	size_t str_pos, new_size;
  
  	GIT_ERROR_CHECK_ALLOC_ADD(&new_size, buf->size, str_len);
  	GIT_ERROR_CHECK_ALLOC_ADD(&new_size, new_size, 1);
  	ENSURE_SIZE(buf, new_size);
  
  	for (str_pos = 0; str_pos < str_len; buf->size++, str_pos++) {
  		if (str[str_pos] == '%' &&
  			str_len > str_pos + 2 &&
  			isxdigit(str[str_pos + 1]) &&
  			isxdigit(str[str_pos + 2])) {
  			buf->ptr[buf->size] = (HEX_DECODE(str[str_pos + 1]) << 4) +
  				HEX_DECODE(str[str_pos + 2]);
  			str_pos += 2;
  		} else {
  			buf->ptr[buf->size] = str[str_pos];
  		}
  	}
  
  	buf->ptr[buf->size] = '\0';
  	return 0;
  }
  
  int git_buf_vprintf(git_buf *buf, const char *format, va_list ap)
  {
  	size_t expected_size, new_size;
  	int len;
  
  	GIT_ERROR_CHECK_ALLOC_MULTIPLY(&expected_size, strlen(format), 2);
  	GIT_ERROR_CHECK_ALLOC_ADD(&expected_size, expected_size, buf->size);
  	ENSURE_SIZE(buf, expected_size);
  
  	while (1) {
  		va_list args;
  		va_copy(args, ap);
  
  		len = p_vsnprintf(
  			buf->ptr + buf->size,
  			buf->asize - buf->size,
  			format, args
  		);
  
  		va_end(args);
  
  		if (len < 0) {
  			git__free(buf->ptr);
  			buf->ptr = git_buf__oom;
  			return -1;
  		}
  
  		if ((size_t)len + 1 <= buf->asize - buf->size) {
  			buf->size += len;
  			break;
  		}
  
  		GIT_ERROR_CHECK_ALLOC_ADD(&new_size, buf->size, len);
  		GIT_ERROR_CHECK_ALLOC_ADD(&new_size, new_size, 1);
  		ENSURE_SIZE(buf, new_size);
  	}
  
  	return 0;
  }
  
  int git_buf_printf(git_buf *buf, const char *format, ...)
  {
  	int r;
  	va_list ap;
  
  	va_start(ap, format);
  	r = git_buf_vprintf(buf, format, ap);
  	va_end(ap);
  
  	return r;
  }
  
  void git_buf_copy_cstr(char *data, size_t datasize, const git_buf *buf)
  {
  	size_t copylen;
  
  	assert(data && datasize && buf);
  
  	data[0] = '\0';
  
  	if (buf->size == 0 || buf->asize <= 0)
  		return;
  
  	copylen = buf->size;
  	if (copylen > datasize - 1)
  		copylen = datasize - 1;
  	memmove(data, buf->ptr, copylen);
  	data[copylen] = '\0';
  }
  
  void git_buf_consume_bytes(git_buf *buf, size_t len)
  {
  	git_buf_consume(buf, buf->ptr + len);
  }
  
  void git_buf_consume(git_buf *buf, const char *end)
  {
  	if (end > buf->ptr && end <= buf->ptr + buf->size) {
  		size_t consumed = end - buf->ptr;
  		memmove(buf->ptr, end, buf->size - consumed);
  		buf->size -= consumed;
  		buf->ptr[buf->size] = '\0';
  	}
  }
  
  void git_buf_truncate(git_buf *buf, size_t len)
  {
  	if (len >= buf->size)
  		return;
  
  	buf->size = len;
  	if (buf->size < buf->asize)
  		buf->ptr[buf->size] = '\0';
  }
  
  void git_buf_shorten(git_buf *buf, size_t amount)
  {
  	if (buf->size > amount)
  		git_buf_truncate(buf, buf->size - amount);
  	else
  		git_buf_clear(buf);
  }
  
  void git_buf_rtruncate_at_char(git_buf *buf, char separator)
  {
  	ssize_t idx = git_buf_rfind_next(buf, separator);
  	git_buf_truncate(buf, idx < 0 ? 0 : (size_t)idx);
  }
  
  void git_buf_swap(git_buf *buf_a, git_buf *buf_b)
  {
  	git_buf t = *buf_a;
  	*buf_a = *buf_b;
  	*buf_b = t;
  }
  
  char *git_buf_detach(git_buf *buf)
  {
  	char *data = buf->ptr;
  
  	if (buf->asize == 0 || buf->ptr == git_buf__oom)
  		return NULL;
  
  	git_buf_init(buf, 0);
  
  	return data;
  }
  
  int git_buf_attach(git_buf *buf, char *ptr, size_t asize)
  {
  	git_buf_dispose(buf);
  
  	if (ptr) {
  		buf->ptr = ptr;
  		buf->size = strlen(ptr);
  		if (asize)
  			buf->asize = (asize < buf->size) ? buf->size + 1 : asize;
  		else /* pass 0 to fall back on strlen + 1 */
  			buf->asize = buf->size + 1;
  	}
  
  	ENSURE_SIZE(buf, asize);
  	return 0;
  }
  
  void git_buf_attach_notowned(git_buf *buf, const char *ptr, size_t size)
  {
  	if (git_buf_is_allocated(buf))
  		git_buf_dispose(buf);
  
  	if (!size) {
  		git_buf_init(buf, 0);
  	} else {
  		buf->ptr = (char *)ptr;
  		buf->asize = 0;
  		buf->size = size;
  	}
  }
  
  int git_buf_join_n(git_buf *buf, char separator, int nbuf, ...)
  {
  	va_list ap;
  	int i;
  	size_t total_size = 0, original_size = buf->size;
  	char *out, *original = buf->ptr;
  
  	if (buf->size > 0 && buf->ptr[buf->size - 1] != separator)
  		++total_size; /* space for initial separator */
  
  	/* Make two passes to avoid multiple reallocation */
  
  	va_start(ap, nbuf);
  	for (i = 0; i < nbuf; ++i) {
  		const char* segment;
  		size_t segment_len;
  
  		segment = va_arg(ap, const char *);
  		if (!segment)
  			continue;
  
  		segment_len = strlen(segment);
  
  		GIT_ERROR_CHECK_ALLOC_ADD(&total_size, total_size, segment_len);
  
  		if (segment_len == 0 || segment[segment_len - 1] != separator)
  			GIT_ERROR_CHECK_ALLOC_ADD(&total_size, total_size, 1);
  	}
  	va_end(ap);
  
  	/* expand buffer if needed */
  	if (total_size == 0)
  		return 0;
  
  	GIT_ERROR_CHECK_ALLOC_ADD(&total_size, total_size, 1);
  	if (git_buf_grow_by(buf, total_size) < 0)
  		return -1;
  
  	out = buf->ptr + buf->size;
  
  	/* append separator to existing buf if needed */
  	if (buf->size > 0 && out[-1] != separator)
  		*out++ = separator;
  
  	va_start(ap, nbuf);
  	for (i = 0; i < nbuf; ++i) {
  		const char* segment;
  		size_t segment_len;
  
  		segment = va_arg(ap, const char *);
  		if (!segment)
  			continue;
  
  		/* deal with join that references buffer's original content */
  		if (segment >= original && segment < original + original_size) {
  			size_t offset = (segment - original);
  			segment = buf->ptr + offset;
  			segment_len = original_size - offset;
  		} else {
  			segment_len = strlen(segment);
  		}
  
  		/* skip leading separators */
  		if (out > buf->ptr && out[-1] == separator)
  			while (segment_len > 0 && *segment == separator) {
  				segment++;
  				segment_len--;
  			}
  
  		/* copy over next buffer */
  		if (segment_len > 0) {
  			memmove(out, segment, segment_len);
  			out += segment_len;
  		}
  
  		/* append trailing separator (except for last item) */
  		if (i < nbuf - 1 && out > buf->ptr && out[-1] != separator)
  			*out++ = separator;
  	}
  	va_end(ap);
  
  	/* set size based on num characters actually written */
  	buf->size = out - buf->ptr;
  	buf->ptr[buf->size] = '\0';
  
  	return 0;
  }
  
  int git_buf_join(
  	git_buf *buf,
  	char separator,
  	const char *str_a,
  	const char *str_b)
  {
  	size_t strlen_a = str_a ? strlen(str_a) : 0;
  	size_t strlen_b = strlen(str_b);
  	size_t alloc_len;
  	int need_sep = 0;
  	ssize_t offset_a = -1;
  
  	/* not safe to have str_b point internally to the buffer */
  	if (buf->size)
  		assert(str_b < buf->ptr || str_b >= buf->ptr + buf->size);
  
  	/* figure out if we need to insert a separator */
  	if (separator && strlen_a) {
  		while (*str_b == separator) { str_b++; strlen_b--; }
  		if (str_a[strlen_a - 1] != separator)
  			need_sep = 1;
  	}
  
  	/* str_a could be part of the buffer */
  	if (buf->size && str_a >= buf->ptr && str_a < buf->ptr + buf->size)
  		offset_a = str_a - buf->ptr;
  
  	GIT_ERROR_CHECK_ALLOC_ADD(&alloc_len, strlen_a, strlen_b);
  	GIT_ERROR_CHECK_ALLOC_ADD(&alloc_len, alloc_len, need_sep);
  	GIT_ERROR_CHECK_ALLOC_ADD(&alloc_len, alloc_len, 1);
  	ENSURE_SIZE(buf, alloc_len);
  
  	/* fix up internal pointers */
  	if (offset_a >= 0)
  		str_a = buf->ptr + offset_a;
  
  	/* do the actual copying */
  	if (offset_a != 0 && str_a)
  		memmove(buf->ptr, str_a, strlen_a);
  	if (need_sep)
  		buf->ptr[strlen_a] = separator;
  	memcpy(buf->ptr + strlen_a + need_sep, str_b, strlen_b);
  
  	buf->size = strlen_a + strlen_b + need_sep;
  	buf->ptr[buf->size] = '\0';
  
  	return 0;
  }
  
  int git_buf_join3(
  	git_buf *buf,
  	char separator,
  	const char *str_a,
  	const char *str_b,
  	const char *str_c)
  {
  	size_t len_a = strlen(str_a),
  		len_b = strlen(str_b),
  		len_c = strlen(str_c),
  		len_total;
  	int sep_a = 0, sep_b = 0;
  	char *tgt;
  
  	/* for this function, disallow pointers into the existing buffer */
  	assert(str_a < buf->ptr || str_a >= buf->ptr + buf->size);
  	assert(str_b < buf->ptr || str_b >= buf->ptr + buf->size);
  	assert(str_c < buf->ptr || str_c >= buf->ptr + buf->size);
  
  	if (separator) {
  		if (len_a > 0) {
  			while (*str_b == separator) { str_b++; len_b--; }
  			sep_a = (str_a[len_a - 1] != separator);
  		}
  		if (len_a > 0 || len_b > 0)
  			while (*str_c == separator) { str_c++; len_c--; }
  		if (len_b > 0)
  			sep_b = (str_b[len_b - 1] != separator);
  	}
  
  	GIT_ERROR_CHECK_ALLOC_ADD(&len_total, len_a, sep_a);
  	GIT_ERROR_CHECK_ALLOC_ADD(&len_total, len_total, len_b);
  	GIT_ERROR_CHECK_ALLOC_ADD(&len_total, len_total, sep_b);
  	GIT_ERROR_CHECK_ALLOC_ADD(&len_total, len_total, len_c);
  	GIT_ERROR_CHECK_ALLOC_ADD(&len_total, len_total, 1);
  	ENSURE_SIZE(buf, len_total);
  
  	tgt = buf->ptr;
  
  	if (len_a) {
  		memcpy(tgt, str_a, len_a);
  		tgt += len_a;
  	}
  	if (sep_a)
  		*tgt++ = separator;
  	if (len_b) {
  		memcpy(tgt, str_b, len_b);
  		tgt += len_b;
  	}
  	if (sep_b)
  		*tgt++ = separator;
  	if (len_c)
  		memcpy(tgt, str_c, len_c);
  
  	buf->size = len_a + sep_a + len_b + sep_b + len_c;
  	buf->ptr[buf->size] = '\0';
  
  	return 0;
  }
  
  void git_buf_rtrim(git_buf *buf)
  {
  	while (buf->size > 0) {
  		if (!git__isspace(buf->ptr[buf->size - 1]))
  			break;
  
  		buf->size--;
  	}
  
  	if (buf->asize > buf->size)
  		buf->ptr[buf->size] = '\0';
  }
  
  int git_buf_cmp(const git_buf *a, const git_buf *b)
  {
  	int result = memcmp(a->ptr, b->ptr, min(a->size, b->size));
  	return (result != 0) ? result :
  		(a->size < b->size) ? -1 : (a->size > b->size) ? 1 : 0;
  }
  
  int git_buf_splice(
  	git_buf *buf,
  	size_t where,
  	size_t nb_to_remove,
  	const char *data,
  	size_t nb_to_insert)
  {
  	char *splice_loc;
  	size_t new_size, alloc_size;
  
  	assert(buf && where <= buf->size && nb_to_remove <= buf->size - where);
  
  	splice_loc = buf->ptr + where;
  
  	/* Ported from git.git
  	 * https://github.com/git/git/blob/16eed7c/strbuf.c#L159-176
  	 */
  	GIT_ERROR_CHECK_ALLOC_ADD(&new_size, (buf->size - nb_to_remove), nb_to_insert);
  	GIT_ERROR_CHECK_ALLOC_ADD(&alloc_size, new_size, 1);
  	ENSURE_SIZE(buf, alloc_size);
  
  	memmove(splice_loc + nb_to_insert,
  		splice_loc + nb_to_remove,
  		buf->size - where - nb_to_remove);
  
  	memcpy(splice_loc, data, nb_to_insert);
  
  	buf->size = new_size;
  	buf->ptr[buf->size] = '\0';
  	return 0;
  }
  
  /* Quote per http://marc.info/?l=git&m=112927316408690&w=2 */
  int git_buf_quote(git_buf *buf)
  {
  	const char whitespace[] = { 'a', 'b', 't', 'n', 'v', 'f', 'r' };
  	git_buf quoted = GIT_BUF_INIT;
  	size_t i = 0;
  	bool quote = false;
  	int error = 0;
  
  	/* walk to the first char that needs quoting */
  	if (buf->size && buf->ptr[0] == '!')
  		quote = true;
  
  	for (i = 0; !quote && i < buf->size; i++) {
  		if (buf->ptr[i] == '"' || buf->ptr[i] == '\\' ||
  			buf->ptr[i] < ' ' || buf->ptr[i] > '~') {
  			quote = true;
  			break;
  		}
  	}
  
  	if (!quote)
  		goto done;
  
  	git_buf_putc(&quoted, '"');
  	git_buf_put(&quoted, buf->ptr, i);
  
  	for (; i < buf->size; i++) {
  		/* whitespace - use the map above, which is ordered by ascii value */
  		if (buf->ptr[i] >= '\a' && buf->ptr[i] <= '\r') {
  			git_buf_putc(&quoted, '\\');
  			git_buf_putc(&quoted, whitespace[buf->ptr[i] - '\a']);
  		}
  
  		/* double quote and backslash must be escaped */
  		else if (buf->ptr[i] == '"' || buf->ptr[i] == '\\') {
  			git_buf_putc(&quoted, '\\');
  			git_buf_putc(&quoted, buf->ptr[i]);
  		}
  
  		/* escape anything unprintable as octal */
  		else if (buf->ptr[i] != ' ' &&
  				(buf->ptr[i] < '!' || buf->ptr[i] > '~')) {
  			git_buf_printf(&quoted, "\\%03o", (unsigned char)buf->ptr[i]);
  		}
  
  		/* yay, printable! */
  		else {
  			git_buf_putc(&quoted, buf->ptr[i]);
  		}
  	}
  
  	git_buf_putc(&quoted, '"');
  
  	if (git_buf_oom(&quoted)) {
  		error = -1;
  		goto done;
  	}
  
  	git_buf_swap(&quoted, buf);
  
  done:
  	git_buf_dispose(&quoted);
  	return error;
  }
  
  /* Unquote per http://marc.info/?l=git&m=112927316408690&w=2 */
  int git_buf_unquote(git_buf *buf)
  {
  	size_t i, j;
  	char ch;
  
  	git_buf_rtrim(buf);
  
  	if (buf->size < 2 || buf->ptr[0] != '"' || buf->ptr[buf->size-1] != '"')
  		goto invalid;
  
  	for (i = 0, j = 1; j < buf->size-1; i++, j++) {
  		ch = buf->ptr[j];
  
  		if (ch == '\\') {
  			if (j == buf->size-2)
  				goto invalid;
  
  			ch = buf->ptr[++j];
  
  			switch (ch) {
  			/* \" or \\ simply copy the char in */
  			case '"': case '\\':
  				break;
  
  			/* add the appropriate escaped char */
  			case 'a': ch = '\a'; break;
  			case 'b': ch = '\b'; break;
  			case 'f': ch = '\f'; break;
  			case 'n': ch = '\n'; break;
  			case 'r': ch = '\r'; break;
  			case 't': ch = '\t'; break;
  			case 'v': ch = '\v'; break;
  
  			/* \xyz digits convert to the char*/
  			case '0': case '1': case '2': case '3':
  				if (j == buf->size-3) {
  					git_error_set(GIT_ERROR_INVALID,
  						"truncated quoted character \\%c", ch);
  					return -1;
  				}
  
  				if (buf->ptr[j+1] < '0' || buf->ptr[j+1] > '7' ||
  					buf->ptr[j+2] < '0' || buf->ptr[j+2] > '7') {
  					git_error_set(GIT_ERROR_INVALID,
  						"truncated quoted character \\%c%c%c",
  						buf->ptr[j], buf->ptr[j+1], buf->ptr[j+2]);
  					return -1;
  				}
  
  				ch = ((buf->ptr[j] - '0') << 6) |
  					((buf->ptr[j+1] - '0') << 3) |
  					(buf->ptr[j+2] - '0');
  				j += 2;
  				break;
  
  			default:
  				git_error_set(GIT_ERROR_INVALID, "invalid quoted character \\%c", ch);
  				return -1;
  			}
  		}
  
  		buf->ptr[i] = ch;
  	}
  
  	buf->ptr[i] = '\0';
  	buf->size = i;
  
  	return 0;
  
  invalid:
  	git_error_set(GIT_ERROR_INVALID, "invalid quoted line");
  	return -1;
  }
  

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