|`class`|This argument should be ignored when used with a class-generic RR type, otherwise `REQUIRE(class == <value>)` should be present at the start of the function.|
|`lexer`|This is used to read the input text stream.|
|`origin`|This is a absolute name used to qualify unqualified / partially qualified domain names in the text stream. It is passed to the name parsing routines.|
|`downcase`|This is passed to the name parsing routines to determine whether to downcase the names it generates or leave them in the case they are presented in.|
|`target`|This is a `BINARY` buffer into which to write the internal format of the rdata record being read.|
`fromtext_typename()` reads tokens from `lexer`,
up to but not including the end of line (EOL) token or end of file (EOF) token.
If the EOL / EOF token is read it should be returned to the input stream.
`gettoken()` should be used to read the next token from the input stream.
`isc_lex_ungettoken()` should be used to return EOL / EOF (or any other token)
to the input stream if the EOL / EOF token is read.
Unused tokens will cause `dns_rdata_fromtext()` to return `DNS_R_EXTRATOKEN` if
`fromtext_typename()` was successful.
`fromtext_typename()` reads external input and as such is a high
security area and must be paranoid about its input.
#### Converting from internal format to text format
|`rdata`|This is the rdata record to be converted from internal format to text. `rdata->type` (and `rdata->class` for class-specific RR types) should be checked at the start of the function with `REQUIRE` statements.|
|`origin`|If this is not `NULL`, then any domain names with this suffix should be written out as unqualified subdomains. `name_prefix()` can be used to check whether `origin` is `NULL` and provide the correct arguments to the name conversion routines.|
|`target`|This is a `TEXT` buffer into which to write the output.|
#### Converting from wire format to internal format
|`class`|This argument should be ignored when used with a class-generic RR type otherwise `REQUIRE(class == <value>)` should be present at the start of the function.|
|`source`|This is a `BINARY` buffer with the `active` region containing a resource record in wire format.|
|`dctx`|This is the decompression context and is passed to `dns_name_fromwire()`, along with `downcase`, to enable a compressed domain name to be extracted from the source.|
|`downcase`|This is passed to `dns_name_fromwire()` to say whether the extracted domain name should be downcased during the extraction.|
|`target`|This is a `BINARY` buffer into which the decompressed and checked resource record is written.|
`fromwire_typename()` is a security sensitive routine
as it reads external data, and should take extreme care to ensure that
the input data matches its description.
If the `active` buffer is not empty at completion and
`fromwire_typename()` was otherwise successful, `dns_rdata_fromwire()`
will return `DNS_R_EXTRADATA`.
#### Converting from internal format to wire format
|`rdata`|This is the rdata record to be converted from internal format to text. `rdata->type` (and `rdata->class` for class-specific RR types) should be checked at the start of the function with `REQUIRE` statements.|
|`cctx`|This is the compression context. It should be passed to `dns_name_towire()` when putting domain names on the wire.|
|`target`|This is a `BINARY` buffer into which to write the rdata|
Simple RR types without domain names can use the following code to
transfer the contents of the `rdata` to the target buffer.
|`class`|This argument should be ignored when used with a class-generic RR type otherwise `REQUIRE(class == <value>)` should be present at the start of the function.|
|`type`|This should be tested with a `REQUIRE(type == <value>)` statement at the beginning of the function.|
|`source`|This points to a type-specific structure.|
|`target`|This is a `BINARY` buffer into which to write the internal format of the rdata record being read in.|
#### Converting from internal format to a structure
|`rdata`|This is the rdata record to be converted from internal format to a structure. `rdata->type` (and `rdata->class` for class-specific RR types) should be checked at the start of the function with `REQUIRE` statements.|
|`target`|Pointer to a type-specific structure.|
#### Comparing two rdata in internal format
static int
compare_typename(dns_rdata_t *rdata1,
dns_rdata_t *rdata2);
static int
compare_classname_typename(dns_rdata_t *rdata1,
dns_rdata_t *rdata2);
This function compares `rdata1` and `rdata2` as required for DNSSEC
ordering. The routine should ensure that the `type` and `class` of the
two rdata match with `REQUIRE(rdata1->type == rdata2->type);` and
`REQUIRE(rdata1->class == rdata2->class);` statements. The
`rdata->type` should also be verified, and if the RR type is
class-specific, also the `rdata->class`.
`compare_classname_typename()` returns -1, 0, 1.
#### Support Functions
The following static support functions are available to use.
