Module wire 

DRDA in the requesting role: the Db2 client’s codec.

Rust owns everything below the SQL: DSS framing (request chains, correlators, continuation segments), DDM objects and their extended lengths, the EBCDIC (CCSID 37) DDM character strings, the package name every SQL command names, and the FD:OCA structures replies carry (SQLCA, SQLDA, the query answer set descriptor and its rows). The model chooses statements and reads decoded results; it never sees or writes a byte of this.

Every length a server declares is checked against what it sent and against a bound of ours before anything is allocated for it: a DSS and its continuations (MAX_DSS_BYTES), a whole reply chain (MAX_REPLY_BYTES, MAX_REPLY_DSS), objects per DSS (MAX_OBJECTS_PER_DSS), columns (MAX_COLUMNS), rows (MAX_ROWS_LIMIT) and the bytes of one answer set (MAX_RESULT_BYTES). None of the decoders recurses.

The layouts follow DRDA (The Open Group, Volume 1) at SQLAM level 7, cross-checked against Apache Derby’s network server and client (org.apache.derby.impl.drda, org.apache.derby.client.net), which is also the server the tests drive.

Modules

cp

DDM code points this client sends or reads.

Structs

Column

One described output column.

Dss

One reply DSS with its continuation segments joined.

Field

One field of an answer-set row: its DRDA type (odd = nullable) and length.

Object

One DDM object.

Package

The package, consistency token and section every SQL command names. When the database name is longer than 18 bytes the extended form (each name preceded by its length) is used.

Repr

How the server represents FD:OCA data: byte order from its TYPDEFNAM, character sets from its TYPDEFOVR.

Sqlca

An SQL communications area: what a statement did.

Enums

Endian

RowItem

One row’s worth of an answer set.

Short

Why a read stopped.

Constants

CCSID_UTF8

CCSID_UTF16

DEFAULT_MAX_ROWS

Rows delivered when max_rows is not given.

DSS_OBJDSS

DSS_RPYDSS

DSS_RQSDSS

DSS types (low nibble of the format byte).

MAX_COLUMNS

A described result may have at most this many columns (Db2’s own limit is 1012).

MAX_CONTINUES

CNTQRY round trips one query may take.

MAX_CREDENTIAL_BYTES

User id and password are DDM strings of at most 255 bytes.

MAX_DSS_BYTES

One reassembled DSS (all its continuation segments joined) may be at most this large.

MAX_OBJECTS_PER_DSS

One DSS may hold at most this many DDM objects.

MAX_RDBNAM_BYTES

A relational database name, with any connection attributes, is at most 255 bytes here.

MAX_REPLY_BYTES

One reply chain — every DSS answering one command — may be at most this large.

MAX_REPLY_DSS

One reply chain may hold at most this many DSSes.

MAX_RESULT_BYTES

The answer-set bytes (QRYDTA) one query may accumulate before it is refused.

MAX_ROWS_LIMIT

The most rows one execute_query may deliver, whatever max_rows asks for.

MAX_SQL_BYTES

The longest statement sent (Db2’s own statement limit is 2 MiB).

OUR_TYPDEFNAM

The data representation this client declares for what it sends: big-endian integers, and through TYPDEFOVR, UTF-8 single-byte and mixed characters.

PKG_COLLECTION

The dynamic-SQL package every statement names: collection NULLID, package SYSLH200 (large, with hold, isolation 2 = cursor stability), consistency token SYSLVL01, section 1. These are the names IBM’s JDBC driver binds; Derby reads isolation and holdability out of them.

PKG_ID

PKG_SECTION

PKG_TOKEN

QUERY_BLOCK_SIZE

The query block size asked for in OPNQRY and CNTQRY.

SECMEC_USRIDONL

USRIDONL: user id only, for a connection with no password.

SECMEC_USRIDPWD

USRIDPWD: user id and password, sent in the clear.

SQLAM_LEVEL

SQLAM level whose FD:OCA layouts this codec reads. A server below it is refused.

Functions

accrdb

ACCRDB: open the database, declaring our data representation and product.

accsec

clsqry

cntqry

command

One command: its DSSes, all under one correlator, chained to each other.

correlation_token

The correlation token DRDA asks a TCP/IP requester for: its IPv4 address as eight hex digits whose first is shifted into G..P, a dot, its port as four hex digits, then six bytes that make this connection’s token unique.

decode_row

Decode the row at the front of buf. Ok(None): the row continues in the next query block.

decode_text

Decode character data in ccsid.

dss

Wrap payload in a DSS, splitting it into continuation segments when it is longer than one segment can say.

ebcdic

Encode a DDM character string in CCSID 37, refusing any character it cannot carry rather than substituting one: a user id or password that arrived altered would be a different credential.

excsat

EXCSAT: who we are and the manager levels we speak.

excsqlimm

EXCSQLIMM + SQLSTT: run a statement that returns no rows.

from_ebcdic

Decode a DDM character string from CCSID 37, trailing blanks dropped.

name_of

The name of a reply message or reply data object, for errors and logs.

object

length | codepoint | data, with an extended length when data does not fit 15 bits.

objects

The objects in one DSS, in order. Extended lengths are honoured; a length running past the DSS is an error.

opnqry

OPNQRY: open the prepared query; the server closes it itself at end of data.

param

params

The parameters inside an object’s data.

parse_qrydsc

Parse the FD:OCA triplets of a QRYDSC (or several, concatenated) into the row layout.

parse_sqlcard

SQLCARD: one SQLCA, or none when the statement succeeded without comment.

parse_sqldard

SQLDARD: the statement’s SQLCA, then its described columns.

prpsqlstt

PRPSQLSTT + SQLSTT: prepare a query and have its output described (extended SQLDA).

rdb_name

RDBNAM as DDM wants it: CCSID 37, at least 18 bytes (blank-padded), at most MAX_RDBNAM_BYTES.

rdbcmm

rdbrllbck

row_object

Pair decoded values with column names into one JSON object per row. Names a statement repeats get #2, #3, …; an unnamed column is COLn.

secchk

secchkcd_meaning

What SECCHKCD says, in words.

severity

SVRCOD of a reply message, 0 when absent.

sqlstt

SQLSTT: a nullable mixed-character LOB (null indicator, 4-byte length, UTF-8 text) then a null single-byte string.

take_dss

Take one complete DSS off the front of buf. Ok(None) means more bytes are needed; an error means the stream is not DRDA, or declares more than MAX_DSS_BYTES.