racket/pkgs/racket-doc/pkg/scribblings/catalog-protocol.scrbl
2016-02-07 13:34:47 -07:00

221 lines
8.5 KiB
Racket

#lang scribble/manual
@(require scribble/bnf
"common.rkt"
(for-label syntax/modcollapse))
@title[#:tag "catalog-protocol"]{Package Catalog Protocol}
A @tech{package catalog} is specified by a URL in one of three
forms:
@itemlist[
@item{@litchar{http://} or @litchar{https://} --- a remote URL}
@item{@litchar{file://} ending with @litchar{.sqlite} --- a local
SQLite database}
@item{@litchar{file://} without @litchar{.sqlite} --- a local
directory}
]
@section{Remote and Directory Catalogs}
In the case of a remote URL or a local directory naming a
@tech{package catalog}, the URL/path is extended as follows to obtain
information about packages:
@itemlist[
@item{@litchar{pkg} and @nonterm{package} path elements, where
@nonterm{package} is a @tech{package name}, plus a
@exec{version=}@nonterm{version} query (where @nonterm{version}
is a Racket version number) in the case of a remote URL.
This URL/path form is used to obtain information about
@nonterm{package}. An HTTP request for a remote URL should
respond with a @racket[read]-able hash table, as described
below. A path in a local directory formed by adding
@filepath{pkg} and @nonterm{package} should refer to a file
that similarly contains a @racket[read]-able hash table.
The hash table should supply the following keys:
@itemlist[
@item{@racket['source] (required) --- a @tech{package source}
string, typically a remote URL. If this source is a
relative URL, then it is treated as relative to the
catalog.
@history[#:changed "6.0.1.7" @elem{Added relative-path support
to clients of a catalog server.}]}
@item{@racket['checksum] (requires) --- a string for a
@tech{checksum}.}
@item{@racket['name] --- a string that is the same as
@nonterm{package}.}
@item{@racket['author] --- a string for the author of the
package, normally an e-mail address.}
@item{@racket['description] --- a string describing the
package.}
@item{@racket['tags] --- a list of strings that describe the
package's categorization.}
@item{@racket['dependencies] --- a list of dependencies for
the package, in the same shape as a @racket[deps]
@filepath{info.rkt} field as described in
@secref["metadata"].}
@item{@racket['modules] --- a list of module paths for modules
that are provided by the package; each module path should
be normalized in the sense of
@racket[collapse-module-path].}
@item{@racket['versions] (optional) --- a hash table mapping
version strings and @racket['default] to hash tables,
where each version-specific hash table provides mappings
to override the ones in the main hash table, and
@racket['default] applies to any version not otherwise
mapped.
Clients of a remote catalog may request information for
a specific version, but they should also check for a
@racket['versions] entry in a catalog response, in case
a catalog with version-specific mappings is implemented
as a directory or by a file-serving HTTP server. A
@racket['default] mapping, meanwhile, allows the main
hash table to provide information that is suitable for
clients at version 5.3.6 and earlier (which do not check
for @racket['versions]).}
]}
@item{@litchar{pkgs} path element: Obtains a list of package names
that are mapped by the @tech{package catalog}. An HTTP request for a remote URL
should respond with a @racket[read]-able list of strings. A
path in a local directory formed by adding @filepath{pkgs}
should refer to a file that similarly
contains a @racket[read]-able list of strings.
This URL/path form is used by @command-ref{catalog-copy} and
tools that allow a user to browse an catalog.
In the case of a local directory, if no @filepath{pkgs} file is
available, a list is created by listing all files in the
@filepath{pkg} directory.}
@item{@litchar{pkgs-all} path element: Obtains a hash table mapping
package names to package details. An HTTP request for a remote
URL should respond with a @racket[read]-able hash table mapping
strings to hash tables. A path in a local directory formed by
adding @filepath{pkgs-all} should refer to a
file that similarly contains a @racket[read]-able hash table.
This URL/path form is a shortcut for a @litchar{pkgs} URL/path
form combined with a @litchar{pkgs/}@nonterm{package} query for
each package.
In the case of a local directory, if no @filepath{pkgs-all}
file is available, a list is created from files in the
@filepath{pkg} directory.}
]
Note that a local directory served as files through an HTTP server
works as a remote URL, as long as the @filepath{pkgs} and
@filepath{pkgs-all} files are present (since those are optional for
local but required for HTTP).
The source for the PLT-hosted @tech{package catalog} is in the
@racket[(collection-file-path "pkg-catalog" "meta")]
directory of the full Racket distribution.
@; ----------------------------------------
@section{SQLite Catalogs}
A SQLite database @tech{package catalog} is meant to be constructed and queries
using the @racketmodname[pkg/db] library, but the database can be
constructed in any way as long as it contains the following tables:
@itemlist[
@item{A @tt{catalog} table with the format
@verbatim[#:indent 2]{(id SMALLINT,
url TEXT,
pos SMALLINT)}
Normally, the only row in this table is @tt{(0, "local", 0)},
but a database that records the content of a set of other
catalogs can also be used as an catalog, in which case each row
represents an catalog; the @tt{id} field is a unique identifier
for each catalog, the @tt{url} field is the catalog's URL, and the
@tt{pos} column orders the catalog relative to others (where a
lower @tt{pos} takes precedence).}
@item{A @tt{pkg} table with the format
@verbatim[#:indent 2]{(name TEXT,
catalog SMALLINT,
author TEXT,
source TEXT,
checksum TEXT,
desc TEXT)}
The @tt{catalog} field is normally @tt{0}; in the case that the
database reflects multiple other catalogs, the @tt{catalog} field
indicates the package entry's source catalog.
The @tt{pkg} and @tt{catalog} fields together determine a unique
row in the table.}
@item{A @tt{tags} table with the form
@verbatim[#:indent 2]{(pkg TEXT,
catalog SMALLINT,
tag TEXT)}
where the @tt{pkg} and @tt{catalog} combination identifies a unique
row in @tt{pkg}.}
@item{A @tt{modules} table with the form
@verbatim[#:indent 2]{(name TEXT,
pkg TEXT,
catalog SMALLINT,
checksum TEXT)}
where the @tt{pkg} and @tt{catalog} combination identifies a unique
row in @tt{pkg}, and @tt{name} is a printed module path.
This table is not currently used by any @exec{raco pkg}
command, but it can be used to suggest package installations to
provide a particular library.}
@item{A @tt{dependencies} table with the form
@verbatim[#:indent 2]{(onpkg TEXT,
onversion TEXT,
onplatform TEXT,
pkg TEXT,
catalog SMALLINT,
checksum TEXT)}
where the @tt{pkg} and @tt{catalog} combination identifies a unique
row in @tt{pkg}, and @tt{onpkg}, @tt{onversion}, and @tt{onplatform}
represent the dependency; @tt{onversion} or @tt{onplatform} is an
empty string if the dependency has no version or platform specification.
This table is not currently used by any @exec{raco pkg}
command.}
]