# Support routines for hand-crafting weird or malicious packs.
#
# You can make a complete pack like:
#
#   pack_header 2 >foo.pack &&
#   pack_obj e69de29bb2d1d6434b8b29ae775ad8c2e48c5391 >>foo.pack &&
#   pack_obj e68fe8129b546b101aee9510c5328e7f21ca1d18 >>foo.pack &&
#   pack_trailer foo.pack

# Print the big-endian 4-byte octal representation of $1
proc uint32_octal {
	setglobal n = $1
	printf '\\%o' $shExpr('$n / 16777216'); setglobal n = $shExpr('n % 16777216')
	printf '\\%o' $shExpr('$n /    65536'); setglobal n = $shExpr('n %    65536')
	printf '\\%o' $shExpr('$n /      256'); setglobal n = $shExpr('n %      256')
	printf '\\%o' $shExpr('$n           ');
}

# Print the big-endian 4-byte binary representation of $1
proc uint32_binary {
	printf $[uint32_octal $1]
}

# Print a pack header, version 2, for a pack with $1 objects
proc pack_header {
	printf 'PACK' &&
	printf '\0\0\0\2' &&
	uint32_binary $1
}

# Print the pack data for object $1, as a delta against object $2 (or as a full
# object if $2 is missing or empty). The output is suitable for including
# directly in the packfile, and represents the entirety of the object entry.
# Doing this on the fly (especially picking your deltas) is quite tricky, so we
# have hardcoded some well-known objects. See the case statements below for the
# complete list.
proc pack_obj {
	match $1 {
	# empty blob
	with e69de29bb2d1d6434b8b29ae775ad8c2e48c5391
		match $2 {
		with ''
			printf '\060\170\234\003\0\0\0\0\1'
			return
			
		}
		

	# blob containing "\7\76"
	with e68fe8129b546b101aee9510c5328e7f21ca1d18
		match $2 {
		with ''
			printf '\062\170\234\143\267\3\0\0\116\0\106'
			return
			
		with 01d7713666f4de822776c7622c10f1b07de280dc
			printf '\165\1\327\161\66\146\364\336\202\47\166' &&
			printf '\307\142\54\20\361\260\175\342\200\334\170' &&
			printf '\234\143\142\142\142\267\003\0\0\151\0\114'
			return
			
		}
		

	# blob containing "\7\0"
	with 01d7713666f4de822776c7622c10f1b07de280dc
		match $2 {
		with ''
			printf '\062\170\234\143\147\0\0\0\20\0\10'
			return
			
		with e68fe8129b546b101aee9510c5328e7f21ca1d18
			printf '\165\346\217\350\22\233\124\153\20\32\356' &&
			printf '\225\20\305\62\216\177\41\312\35\30\170\234' &&
			printf '\143\142\142\142\147\0\0\0\53\0\16'
			return
			
		}
		
	}

	echo >&2 "BUG: don't know how to print $1$(2:+ (from $2))> !2 "BUG: don't know how to print $1${2:+ (from $2)}"
	return 1
}

# Compute and append pack trailer to "$1"
proc pack_trailer {
	test-sha1 -b <$1 >trailer.tmp &&
	cat trailer.tmp >>$1 &&
	rm -f trailer.tmp
}

# Remove any existing packs to make sure that
# whatever we index next will be the pack that we
# actually use.
proc clear_packs {
	rm -f .git/objects/pack/*
}