Low Level Filesystem Access - Revision history

Jhoger: /* Published ROM Calls for Manipulating RAM Files */

2009-04-14T22:10:35Z

Published ROM Calls for Manipulating RAM Files

← Older revision		Revision as of 15:10, 14 April 2009
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	The routine '''MASDEL''', called at 6B9F, deletes a specified number of characters from a file. Prior to a call, BC must contain the number of characters to be deleted, and HL should point to the address at which to begin deleting. HL and BC are preserved.		The routine '''MASDEL''', called at 6B9F, deletes a specified number of characters from a file. Prior to a call, BC must contain the number of characters to be deleted, and HL should point to the address at which to begin deleting. HL and BC are preserved.

			The routine '''PRSNAM''' parses a filename pointed to by HL, length in E, and puts the result in FILNAM.

			The routine '''SRCNAM''' searches the directory for the name stored at FILNAM. On exit, HL points to the entry and A contains the directory flag value. Z is set if file is not found.

	== LNKFIL ==		== LNKFIL ==

Jhoger: /* File List/Pointer Cache */

2009-04-14T15:56:57Z

File List/Pointer Cache

← Older revision		Revision as of 08:56, 14 April 2009
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	\| 1 for invisible file		\| 1 for invisible file
	\|-		\|-
	\| 2-1		\| 2
	\| Reserved		\| Reserved
			\|-
			\| 1
			\| For DO files, true indicates "opened"
	\|-		\|-
	\| 0		\| 0

Jhoger: /* Published ROM Calls for Manipulating RAM Files */

2009-04-11T23:53:59Z

Published ROM Calls for Manipulating RAM Files

← Older revision		Revision as of 16:53, 11 April 2009
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	Upon exiting the routine, the HL register points to the TOP address of the new file (the address at which new characters would be added), and DE points to the address of the directory file flag, located somewhere in the directory starting at F962.		Upon exiting the routine, the HL register points to the TOP address of the new file (the address at which new characters would be added), and DE points to the address of the directory file flag, located somewhere in the directory starting at F962.

	The routine '''CHKDC''', called at 5AA9, examines the directory to determine if a specified filename is present in the directory as a valid file. Prior to the call, DE should point to the first in a series of memory addresses (RAM or ROM) containing a filename in ASCII followed by a null.		The routine '''CHKDC''', called at 5AA9, examines the directory to determine if a specified filename is present in the directory as a valid file. Prior to the call, DE should point to the first in a series of memory addresses (RAM or ROM) containing a filename in ASCII followed by a null. Note that CHKDC modifies ALTLCD.

			Rather than CHKDC, you may prefer to call the alternative FINDFL routine at $20AF. Instead of a NUL terminated string, you must supply a space-padded string with the extension right-justified as is normal when using the FILNAM buffer. One particular benefit is that unlike CHKDC, FINDFL does not poke around in ALTLCD.

	([[User:Jhoger\|Jhoger]] 22:39, 4 April 2009 (PDT) note: I've found that I need to call '''LNKFIL''' before calling '''CHKDC''' if the file I want to access was recently created by SAVEM)		([[User:Jhoger\|Jhoger]] 22:39, 4 April 2009 (PDT) note: I've found that I need to call '''LNKFIL''' before calling '''CHKDC''' if the file I want to access was recently created by SAVEM)

Jhoger: /* LNKFIL */

2009-04-11T21:20:32Z

LNKFIL

← Older revision		Revision as of 14:20, 11 April 2009
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	# The file section pointers must be accurate		# The file section pointers must be accurate
	# The order ~~of files~~ in ~~the directory must match~~ the order of files in RAM		# The directory entries, though out of order and never actually sorted, if sorted by start address MUST ALWAYS result in an identical ordering to the order of actual files in RAM.

	LNKFIL is dependent on the file section pointers:		LNKFIL is dependent on the file section pointers:
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	To maintain accuracy of section pointers, follow the discipline of only using MAKHOL or MASDEL to wedge open space or remove file bytes, respectively, rather than attempting to do it in some ad hoc fashion.		To maintain accuracy of section pointers, follow the discipline of only using MAKHOL or MASDEL to wedge open space or remove file bytes, respectively, rather than attempting to do it in some ad hoc fashion.

	To avoid corrupting the RAM filesystem, make sure to call LNKFIL before looking up a file entry if there is any chance that the filesystem has been modified without a fixup by LNKFIL. Also, ~~upon allocation~~ of a ~~new directory entry~~, ~~ensure that you wedge open~~ the ~~correct spot relative to other files~~ of the ~~same type~~ to ~~maintain~~ the ~~order~~.		To avoid corrupting the RAM filesystem, make sure to call LNKFIL before looking up a file entry if there is any chance that the filesystem has been modified without a fixup by LNKFIL. Also, always add a file to the end of a given file section. Basically, call MAKHOL with the value of the pointer to the subsequent section.

	== File Creation ==		== File Creation ==

Jhoger: /* Published ROM Calls for Manipulating RAM Files */

2009-04-11T21:16:53Z

Published ROM Calls for Manipulating RAM Files

← Older revision		Revision as of 14:16, 11 April 2009
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	The routine '''MAKHOL''', called at 6B6D, inserts a specified number of spaces in a file. Everything is moved up in memory to accommodate the spaces. These spaces may later be changed as desired. Prior to the call, BC must contain the number of spaces to be inserted, and HL must point to the address at which to insert the spaces. HL and BC are preserved, which is handy. If there was insufficient room in RAM, the routine returns with the carry flag set.		The routine '''MAKHOL''', called at 6B6D, inserts a specified number of spaces in a file. Everything is moved up in memory to accommodate the spaces. These spaces may later be changed as desired. Prior to the call, BC must contain the number of spaces to be inserted, and HL must point to the address at which to insert the spaces. HL and BC are preserved, which is handy. If there was insufficient room in RAM, the routine returns with the carry flag set.

	The routine '''MASDEL''', called at 6B9F, deletes a specified number of characters from a file. Prior to a call, BC must ~~containt~~ the number of characters to be deleted, and HL should point to the address at which to begin deleting. HL and BC are preserved.		The routine '''MASDEL''', called at 6B9F, deletes a specified number of characters from a file. Prior to a call, BC must contain the number of characters to be deleted, and HL should point to the address at which to begin deleting. HL and BC are preserved.

	== LNKFIL ==		== LNKFIL ==

Jhoger: /* Published ROM Calls for Manipulating RAM Files */

2009-04-11T21:16:33Z

Published ROM Calls for Manipulating RAM Files

← Older revision		Revision as of 14:16, 11 April 2009
Line 154:		Line 154:

	The routine '''MAKHOL''', called at 6B6D, inserts a specified number of spaces in a file. Everything is moved up in memory to accommodate the spaces. These spaces may later be changed as desired. Prior to the call, BC must contain the number of spaces to be inserted, and HL must point to the address at which to insert the spaces. HL and BC are preserved, which is handy. If there was insufficient room in RAM, the routine returns with the carry flag set.		The routine '''MAKHOL''', called at 6B6D, inserts a specified number of spaces in a file. Everything is moved up in memory to accommodate the spaces. These spaces may later be changed as desired. Prior to the call, BC must contain the number of spaces to be inserted, and HL must point to the address at which to insert the spaces. HL and BC are preserved, which is handy. If there was insufficient room in RAM, the routine returns with the carry flag set.

	~~A note on MAKHOL: MAKHOL damages the BINTAB ($FBB0) variable, which indicates the start of the CO files in memory. So, you must preserve and restore it across calls to MAKHOL.~~

	The routine '''MASDEL''', called at 6B9F, deletes a specified number of characters from a file. Prior to a call, BC must containt the number of characters to be deleted, and HL should point to the address at which to begin deleting. HL and BC are preserved.		The routine '''MASDEL''', called at 6B9F, deletes a specified number of characters from a file. Prior to a call, BC must containt the number of characters to be deleted, and HL should point to the address at which to begin deleting. HL and BC are preserved.

Jhoger: /* Published ROM Calls for Manipulating RAM Files */

2009-04-11T20:48:02Z

Published ROM Calls for Manipulating RAM Files

← Older revision		Revision as of 13:48, 11 April 2009
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	The routine '''MAKHOL''', called at 6B6D, inserts a specified number of spaces in a file. Everything is moved up in memory to accommodate the spaces. These spaces may later be changed as desired. Prior to the call, BC must contain the number of spaces to be inserted, and HL must point to the address at which to insert the spaces. HL and BC are preserved, which is handy. If there was insufficient room in RAM, the routine returns with the carry flag set.		The routine '''MAKHOL''', called at 6B6D, inserts a specified number of spaces in a file. Everything is moved up in memory to accommodate the spaces. These spaces may later be changed as desired. Prior to the call, BC must contain the number of spaces to be inserted, and HL must point to the address at which to insert the spaces. HL and BC are preserved, which is handy. If there was insufficient room in RAM, the routine returns with the carry flag set.

	A note on MAKHOL: MAKHOL damages the BINTAB variable, which indicates the start of the CO files in memory. So, you must preserve and restore it across calls to MAKHOL.		A note on MAKHOL: MAKHOL damages the BINTAB ($FBB0) variable, which indicates the start of the CO files in memory. So, you must preserve and restore it across calls to MAKHOL.

	The routine '''MASDEL''', called at 6B9F, deletes a specified number of characters from a file. Prior to a call, BC must containt the number of characters to be deleted, and HL should point to the address at which to begin deleting. HL and BC are preserved.		The routine '''MASDEL''', called at 6B9F, deletes a specified number of characters from a file. Prior to a call, BC must containt the number of characters to be deleted, and HL should point to the address at which to begin deleting. HL and BC are preserved.

Jhoger: /* Published ROM Calls for Manipulating RAM Files */

2009-04-11T20:47:41Z

Published ROM Calls for Manipulating RAM Files

← Older revision		Revision as of 13:47, 11 April 2009
Line 154:		Line 154:

	The routine '''MAKHOL''', called at 6B6D, inserts a specified number of spaces in a file. Everything is moved up in memory to accommodate the spaces. These spaces may later be changed as desired. Prior to the call, BC must contain the number of spaces to be inserted, and HL must point to the address at which to insert the spaces. HL and BC are preserved, which is handy. If there was insufficient room in RAM, the routine returns with the carry flag set.		The routine '''MAKHOL''', called at 6B6D, inserts a specified number of spaces in a file. Everything is moved up in memory to accommodate the spaces. These spaces may later be changed as desired. Prior to the call, BC must contain the number of spaces to be inserted, and HL must point to the address at which to insert the spaces. HL and BC are preserved, which is handy. If there was insufficient room in RAM, the routine returns with the carry flag set.

			A note on MAKHOL: MAKHOL damages the BINTAB variable, which indicates the start of the CO files in memory. So, you must preserve and restore it across calls to MAKHOL.

	The routine '''MASDEL''', called at 6B9F, deletes a specified number of characters from a file. Prior to a call, BC must containt the number of characters to be deleted, and HL should point to the address at which to begin deleting. HL and BC are preserved.		The routine '''MASDEL''', called at 6B9F, deletes a specified number of characters from a file. Prior to a call, BC must containt the number of characters to be deleted, and HL should point to the address at which to begin deleting. HL and BC are preserved.

Jhoger: /* File List/Pointer Cache */

2009-04-11T20:45:35Z

File List/Pointer Cache

← Older revision		Revision as of 13:45, 11 April 2009
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	Notice that no entry exists for filesize. To determine filesize, either of two techniques may be used. By comparing the various start addresses, one can determine the next file's starting address. The two start addresses may simply be subtracted.		Notice that no entry exists for filesize. To determine filesize, either of two techniques may be used. By comparing the various start addresses, one can determine the next file's starting address. The two start addresses may simply be subtracted.

	However, the filenames in the directory are not~~, in the simplest sense,~~ in order by start address, so one must search the entire directory to find the next file up. The ending address of the top file is stored at FBB2+. This is not strictly true: for each given file type (BA, DO, CO) valid directory entries are always in exactly the same order as the actual files in memory. It is only when they are considered as a mixture of different types that order differs.		However, the filenames in the directory are not in order by start address, so one must search the entire directory to find the next file up. The ending address of the top file is stored at FBB2+.

	Another way to determine file size is by examining the files themselves, since the file itself always contains enough information to determine its size. With BA and DO files, you must scan the file, beginning at the start address, to locate the end-of-file marker. For DO files, the EOF characters is $1A (26 decimal). For BA files, it is a three character sequence, 00H,00H,00H.		Another way to determine file size is by examining the files themselves, since the file itself always contains enough information to determine its size. With BA and DO files, you must scan the file, beginning at the start address, to locate the end-of-file marker. For DO files, the EOF characters is $1A (26 decimal). For BA files, it is a three character sequence, 00H,00H,00H.

99.6.119.22: /* File Creation */

2009-04-11T03:29:17Z

File Creation

← Older revision		Revision as of 20:29, 10 April 2009
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	* BASIC files (BA)		* BASIC files (BA)
	* Text files (DO)		* Text files (DO)
	* Machine language files		* Machine language files (CO)
	* The three scratch pads (Suzuki, Hayashi, RickY)		* The three scratch pads (Suzuki, Hayashi, RickY)