Filetable Module Interface Specification

Informal Introduction

File table is a global system table. It contains one entry for each file in a
system. Such entry is identified by its position in a table; it contains i-node
number of the corresponding file and a current position in the file. File reference
count corresponds to the number of times file has been opened (and not yet closed);
file reference count is decremented each time the file is closed and the file table
entry is removed when the reference count is decremented to zero.

(0) CHARACTERISTICS

-type specified: filetable

-features: non-deterministic, non-parameterized

-foreign types: global

(1) SYNTAX

ACCESS-PROGRAMS

Program Name	Arg#1	Arg#2	Arg#3	Arg#4	Result Type
CREATE	filetable:VO	int:VR	int:V	int:V
SETPOS	filetable:VO	int:V	int:V
INCCOUNTER	filetable:VO	int:V
DECCOUNTER	filetable:VO	int:V
GETINODETABLEINDEX	filetable:V	int:V			int
GETPOS	filetable:V	int:V			int
EXISTS	filetable:V	int:V			bool
ISFULL	filetable:V				bool

(2) CANONICAL TRACES

canonical(T)

n:<int>; m[0]..m[n], k[0]..k[n], pos[0]..pos[n], in[0]..in[n], c[0]..c[n]:<int>0 - 1

n < global::G_filetable_size()

k[0]

i:<int>0

n [0 - 1

m[i]

pos[i]

pos[i] < global::G_sequence_size()

in[i]

in[i] < global::G_inodetable_size())

(i < n

k[i] < k[i + 1]))] [T = [CREATE(*, (*1,c[i])

k[i], pos[i], in[i]).[INCCOUNTER(*, k[i])]j=0..m[i]]i=0..n ]

AUXILIARY FUNCTIONS

interrorval: <int>

interrorval() = -1

filetablesize: <filetable> <int>

filetablesize(FT) =

Condition	Value
FT = _	0
! FT1:<filetable>; k,m,pos,in,c:<int>0 k (0 - 1 m 0 pos 0 in) [FT = FT1.CREATE(, (1,c) k, pos, in).[INCCOUNTER(*, k)]i=0..m ]	k + 1

isfull: <filetable> <bool>

isfull(FT) = count(FT, "CREATE") = global::G_filetable_size()

getcounter: <filetable> × <int> <int>

getcounter(FT, k) =

Condition	Value
k < 0 k global::G_filetable_size()	interrorval()
Ź ! FT1,FT2:<filetable>; m,pos,in,c:<int>0 - 1 m 0 pos 0 in [FT = FT1.CREATE(, (1,c) k, pos, in).[INCCOUNTER(, k)]i=0..m.FT2 0 k k < global::G_filetable_size*()]	0
! FT1,FT2:<filetable>; m,pos,in,c:<int>0 - 1 m 0 pos 0 in [FT = FT1.CREATE(, (1,c) k, pos, in).[INCCOUNTER(, k)]i=0..m.FT2 0 k k < global::G_filetable_size*()]	m + 2

exists: <filetable> × <int> <bool>

exists(FT, k) = getcounter(FT, k) 1

getpos: <filetable> × <int> <int>

getpos(FT, k) =

Condition	Value
Źexists(FT, k)	interrorval()
exists(FT, k)	pos where FT1,FT2:<filetable>; m,pos,in,c:<int> [0 - 1 m 0 pos 0 in FT = FT1.CREATE(, (1,c) k, pos, in).[INCCOUNTER(*, k)]i=0..m.FT2 ]

getinodetableindex: <filetable> × <int> <int>

getinodetableindex(FT, k) =

Condition	Value
Źexists(FT, k)	interrorval()
exists(FT, k)	in where FT1,FT2:<filetable>; m,pos,in,c:<int> [0 - 1 m 0 pos 0 in FT = FT1.CREATE(, (1,c) k, pos, in).[INCCOUNTER(*, k)]i=0..m.FT2 ]

(3) SEMANTICS

ACCESS-PROGRAMS

Legality(CREATE((n, FT), (k, C), pos, in)) =

Condition	Value
0 pos pos < global::G_sequence_size() (0 in in < global::G_inodetable_size()) Źisfull(FT)	%legal%
Ź(0 pos pos < global::G_sequence_size() (0 in in < global::G_inodetable_size())) Źisfull(FT)	%invalid argument%
0 pos pos < global::G_sequence_size() (0 in in < global::G_inodetable_size()) isfull(FT)	%no more free positions%

CREATE((n, FT) , (k, C) k0, pos, in) = FT1.CREATE(*, (*1,C) k0, pos, in).FT2 where FT1,FT2:<filetable> [FT = FT1.FT2 canonical(FT1.CREATE(*, (*1,C) k0, pos, in).FT2)]

CREATE((n, FT), (k, C) k0, pos, in) | Źexists(FT, k0)

Legality(SETPOS((n, FT), k, pos)) =

Condition	Value
k < 0 k global::G_filetable_size() pos < 0 pos global::G_sequence_size()	%invalid argument%
0 k k < global::G_filetable_size() (0 pos pos < global::G_sequence_size() Źexists(FT, k))	%referenced file table position doesn't exists%
0 pos pos < global::G_sequence_size() exists(FT, k)	%legal%

SETPOS((n, FT) , k, pos) = newFT where FT1,FT2,newFT:<filetable>; m,p,in,c:<int> [0 - 1 m 0 p 0 in (FT = FT1.CREATE(*, (*1,c) k, p, in).[INCCOUNTER(*, k)]i=0..m.FT2 newFT = FT1.CREATE(*, (*1,c) k, pos, in).[INCCOUNTER(*, k)]i=0..m.FT2 )]

Legality(INCCOUNTER((n, FT), k)) =

Condition	Value
k < 0 k global::G_filetable_size()	%invalid argument%
0 k k < global::G_filetable_size() Źexists(FT, k)	%referenced file table position doesn't exists%
exists(FT, k)	%legal%

INCCOUNTER((n, FT) , k) = newFT where FT1,FT2,newFT:<filetable>; m,pos,in,c:<int> [0 - 1 m 0 pos 0 in (FT = FT1.CREATE(*, (*1,c) k, pos, in).[INCCOUNTER(*, k)]i=0..m.FT2 newFT = FT1.CREATE(*, (*1,c) k, pos, in).[INCCOUNTER(*, k)]i=0..m + 1.FT2 )]

Legality(DECCOUNTER((n, FT), k)) =

Condition	Value
k < 0 k global::G_filetable_size()	%invalid argument%
0 k k < global::G_filetable_size() Źexists(FT, k)	%referenced file table position doesn't exists%
exists(FT, k)	%legal%

DECCOUNTER((n, FT) , k) =

Condition	Value
! m:<int>m 0 [FT = FT1.CREATE(, (1,c) k, pos, in).[INCCOUNTER(*, k)]i=0..m.FT2 ]	FT1.CREATE(, (1,c) k, pos, in).[INCCOUNTER(*, k)]i=0..m - 1.FT2
FT = FT1.CREATE(, (1,c) k, pos, in).FT2	FT1.FT2

where FT1,FT2:<filetable>; pos,in,c:<int> [0

pos

in]

Legality(GETINODETABLEINDEX(FT, k)) = %legal%

GETINODETABLEINDEX(FT, k) = getinodetableindex(FT, k)

Legality(GETPOS(FT, k)) = %legal%

GETPOS(FT, k) = getpos(FT, k)

Legality(EXISTS(FT, k)) = %legal%

EXISTS(FT, k) = exists(FT, k)

Legality(ISFULL(FT)) = %legal%

ISFULL(FT) = isfull(FT)