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.\" $Id: elftc_string_table_create.3 3750 2019-06-28 01:12:10Z emaste $
.\"
.Dd June 27, 2019
.Dt ELFTC_STRING_TABLE_CREATE 3
.Os
.Sh NAME
.Nm elftc_string_table_create ,
.Nm elftc_string_table_destroy ,
.Nm elftc_string_table_from_section ,
.Nm elftc_string_table_image ,
.Nm elftc_string_table_insert ,
.Nm elftc_string_table_lookup ,
.Nm elftc_string_table_remove ,
.Nm elftc_string_table_to_string
.Nd convenience routines for handling ELF string tables
.Sh SYNOPSIS
.In libelftc.h
.Ft "Elftc_String_Table *"
.Fn elftc_string_table_create "size_t sizehint"
.Ft void
.Fn elftc_string_table_destroy "Elftc_String_Table *table"
.Ft "Elftc_String_Table *"
.Fn elftc_string_table_from_section "Elf_Scn *scn" "size_t sizehint"
.Ft "const char *"
.Fo elftc_string_table_image
.Fa "Elftc_String_Table *table"
.Fa "size_t *size"
.Fc
.Ft size_t
.Fo elftc_string_table_insert
.Fa "Elftc_String_Table *table"
.Fa "const char *string"
.Fc
.Ft size_t
.Fo elftc_string_table_lookup
.Fa "Elftc_String_Table *table"
.Fa "const char *string"
.Fc
.Ft int
.Fo elftc_string_table_remove
.Fa "Elftc_String_Table *table"
.Fa "const char *string"
.Fc
.Ft "const char *"
.Fo elftc_string_table_to_string
.Fa "Elftc_String_Table *table"
.Fa "size_t offset"
.Fc
.Sh DESCRIPTION
This manual page documents convenience routines for handling ELF
string tables.
.Pp
Function
.Fn elftc_string_table_create
creates a new, empty string table.
The argument
.Ar sizehint
provides a hint about the expected number of bytes of string data in
the table.
If the argument
.Ar sizehint
is zero, an implementation-defined default will be used instead.
.Pp
Function
.Fn elftc_string_table_destroy
destroys the previously allocated string table specified by
argument
.Ar table ,
and frees the internal resources allocated for it.
.Pp
Function
.Fn elftc_string_table_from_section
creates a new string table and initializes it based on the
contents of the section specified by argument
.Ar scn .
This section must be of type
.Dv SHT_STRTAB .
The argument
.Ar sizehint
provides a hint about expected number of bytes of string data in the
table.
If the value of
.Ar sizehint
is zero, an implementation-default will be used instead.
.Pp
Function
.Fn elftc_string_table_image
returns a pointer to the ELF representation of the contents of the
string table specified by argument
.Ar table .
If argument
.Ar size
is not NULL, the size of the ELF representation of the string table is
stored in the location pointed to by argument
.Ar size .
The function
.Fn elftc_string_table_image
will compact the string table if the table contains deleted strings.
The string offsets returned by prior calls to
.Fn elftc_string_table_insert
and
.Fn elftc_string_table_lookup
should be treated as invalid after a call to this function.
.Pp
Function
.Fn elftc_string_table_insert
inserts the NUL-terminated string pointed to by argument
.Ar string
into the string table specified by argument
.Ar table ,
and returns an offset value usable in ELF data structures.
Multiple insertions of the same content will return the same offset.
The offset returned will remain valid until the next call to
.Fn elftc_string_table_image .
.Pp
Function
.Fn elftc_string_table_lookup
looks up the string referenced by argument
.Ar string
in the string table specified by argument
.Ar table ,
and if found, returns the offset associated with the string.
The returned offset will be valid until the next call to
.Fn elftc_string_table_image .
.Pp
Function
.Fn elftc_string_table_remove
removes the string pointed by argument
.Ar string
from the string table referenced by argument
.Ar table ,
if it is present in the string table.
.Pp
Function
.Fn elftc_string_table_to_string
returns a pointer to the NUL-terminated string residing at argument
.Ar offset
in the string table specified by argument
.Ar table .
The value of argument
.Ar offset
should be one returned by a prior call to
.Fn elftc_string_table_insert
or
.Fn elftc_string_table_lookup .
The returned pointer will remain valid until the next call to
.Fn elftc_string_table_insert
or
.Fn elftc_string_table_image .
.Ss Memory Management
The
.Lb libelftc
library manages its own memory allocations.
The application should not free the pointers returned by the string
table functions.
.Sh IMPLEMENTATION NOTES
The current implementation is optimized for the case where strings are
added to a string table, but rarely removed from it.
.Pp
The functions
.Fn elftc_string_table_insert ,
.Fn elftc_string_table_lookup ,
.Fn elftc_string_table_remove
and
.Fn elftc_string_table_to_string
have O(1) asymptotic behavior.
The function
.Fn elftc_string_table_image
can have O(size) asymptotic behavior, where
.Ar size
denotes the size of the string table.
.Sh RETURN VALUES
Functions
.Fn elftc_string_table_create
and
.Fn elftc_string_table_from_section
return a valid pointer to an opaque structure of type
.Vt Elftc_String_Table
on success, or NULL in case of an error.
.Pp
The function
.Fn elftc_string_table_image
returns a pointer to an in-memory representation of an ELF string
table on success, or NULL in case of an error.
.Pp
Functions
.Fn elftc_string_table_insert
and
.Fn elftc_string_table_lookup
return a non-zero offset on success, or zero in case of an error.
.Pp
Function
.Fn elftc_string_table_remove
returns a positive value on success, or zero in case of an error.
.Pp
Function
.Fn elftc_string_table_to_string
returns a valid pointer on success, or NULL in case of an error.
.Sh SEE ALSO
.Xr dwarf 3 ,
.Xr elf 3 ,
.Xr elftc 3