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SAR$ WRITE
• Image buffer
The image buffer is used to construct individual images from information in the text
buffer and attribute table and move them into the output buffer. Because images
can be written in different formats, this buffer is necessary to relieve the calling
program from having to build these formats. The calling program never needs to
access the image buffer, but it must provide it to SAR$. The calling program using
the READ and WRITE functions of SAR$ can use the same image buffer for both
functions.
• Text buffer
The text buffer is used to pass the characters of the output image to SAR$. The
calling program must place the characters sequentially in the text buffer, regardless
of the eventual output format or attributes that may apply to the characters. The
text buffer is one part of internal format (see 16.2). The calling program using the
READ and WRITE functions of SAR$ can use the same text buffer for both
functions.
• Attribute table
The attribute table is used to pass to SAR$ the attributes that apply to the characters
in the text buffer. Each attribute has a one-word entry in the attribute table which
follows the format in Figure 18–1.
index type value
0 17 18 26 27 35
Figure 18–1. SAR$: Attribute Table Entry
The calling program places the attribute entries into the attribute table. The attribute
table is the other part of internal format (see 16.2). If the output images will not
contain any attributes or if UNTRANSLATE_MODE is set to S (on), the attribute table
may be omitted by setting ATTRIBUTE_TABLE_ADDRESS to null (zero). The calling
program using the READ and WRITE functions of SAR$ can use the same attribute
table for both functions.
All buffers and tables must be provided by the calling program. The type definitions for
the buffers and tables and definitions for the default buffer and table lengths are
contained in the element SAR$DEFN in the SYSLIB file (SYS$LIB$*SYSLIB) or
SYS$*RLIB$. They may be obtained with the COPY statement. These definitions
simplify the creation of required buffers and tables for the calling program.
7833 1733–004 18–11