reference: make some regexp vars a const, remove intermediate vars

This patch:

- makes regexp strings that are constant a const
- moves some variables closer to where they're used
- removes some intermediate vars
- un-wraps some lines; they're lengthy, but probably more readable than having
  them wrapped over multiple lines.
- touches-up some docs.

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>
This commit is contained in:
Sebastiaan van Stijn 2022-11-08 16:52:02 +01:00
parent 10eace9a53
commit 226b21beb6
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@ -2,13 +2,13 @@ package reference
import "regexp"
var (
// alphaNumeric defines the alpha numeric atom, typically a
const (
// alphanumeric defines the alphanumeric atom, typically a
// component of names. This only allows lower case characters and digits.
alphaNumeric = `[a-z0-9]+`
alphanumeric = `[a-z0-9]+`
// separator defines the separators allowed to be embedded in name
// components. This allow one period, one or two underscore and multiple
// components. This allows one period, one or two underscore and multiple
// dashes. Repeated dashes and underscores are intentionally treated
// differently. In order to support valid hostnames as name components,
// supporting repeated dash was added. Additionally double underscore is
@ -16,33 +16,43 @@ var (
// supported names.
separator = `(?:[._]|__|[-]*)`
// nameComponent restricts registry path component names to start
// with at least one letter or number, with following parts able to be
// separated by one period, one or two underscore and multiple dashes.
nameComponent = expression(
alphaNumeric,
optional(repeated(separator, alphaNumeric)))
// domainNameComponent restricts the registry domain component of a
// repository name to start with a component as defined by DomainRegexp.
domainNameComponent = `(?:[a-zA-Z0-9]|[a-zA-Z0-9][a-zA-Z0-9-]*[a-zA-Z0-9])`
// tag matches valid tag names. From docker/docker:graph/tags.go.
tag = `[\w][\w.-]{0,127}`
// digestPat matches well-formed digests, including algorithm (e.g. "sha256:<encoded>").
//
// TODO(thaJeztah): this should follow the same rules as https://pkg.go.dev/github.com/opencontainers/go-digest@v1.0.0#DigestRegexp
// so that go-digest defines the canonical format. Note that the go-digest is
// more relaxed:
// - it allows multiple algorithms (e.g. "sha256+b64:<encoded>") to allow
// future expansion of supported algorithms.
// - it allows the "<encoded>" value to use urlsafe base64 encoding as defined
// in [rfc4648, section 5].
//
// [rfc4648, section 5]: https://www.rfc-editor.org/rfc/rfc4648#section-5.
digestPat = `[A-Za-z][A-Za-z0-9]*(?:[-_+.][A-Za-z][A-Za-z0-9]*)*[:][[:xdigit:]]{32,}`
// identifier is the format for a content addressable identifier using sha256.
// These identifiers are like digests without the algorithm, since sha256 is used.
identifier = `([a-f0-9]{64})`
// ipv6address are enclosed between square brackets and may be represented
// in many ways, see rfc5952. Only IPv6 in compressed or uncompressed format
// are allowed, IPv6 zone identifiers (rfc6874) or Special addresses such as
// IPv4-Mapped are deliberately excluded.
ipv6address = expression(
literal(`[`), `(?:[a-fA-F0-9:]+)`, literal(`]`),
)
ipv6address = `\[(?:[a-fA-F0-9:]+)\]`
)
var (
// domainName defines the structure of potential domain components
// that may be part of image names. This is purposely a subset of what is
// allowed by DNS to ensure backwards compatibility with Docker image
// names. This includes IPv4 addresses on decimal format.
domainName = expression(
domainNameComponent,
optional(repeated(literal(`.`), domainNameComponent)),
)
domainName = expression(domainNameComponent, optional(repeated(literal(`.`), domainNameComponent)))
// host defines the structure of potential domains based on the URI
// Host subcomponent on rfc3986. It may be a subset of DNS domain name,
@ -53,69 +63,63 @@ var (
// allowed by the URI Host subcomponent on rfc3986 to ensure backwards
// compatibility with Docker image names.
domain = expression(
host,
optional(literal(`:`), `[0-9]+`))
domain = expression(host, optional(literal(`:`), `[0-9]+`))
// DomainRegexp defines the structure of potential domain components
// that may be part of image names. This is purposely a subset of what is
// allowed by DNS to ensure backwards compatibility with Docker image
// names.
// DomainRegexp matches hostname or IP-addresses, optionally including a port
// number. It defines the structure of potential domain components that may be
// part of image names. This is purposely a subset of what is allowed by DNS to
// ensure backwards compatibility with Docker image names. It may be a subset of
// DNS domain name, an IPv4 address in decimal format, or an IPv6 address between
// square brackets (excluding zone identifiers as defined by [rfc6874] or special
// addresses such as IPv4-Mapped).
//
// [rfc6874]: https://www.rfc-editor.org/rfc/rfc6874.
DomainRegexp = regexp.MustCompile(domain)
tag = `[\w][\w.-]{0,127}`
// TagRegexp matches valid tag names. From docker/docker:graph/tags.go.
TagRegexp = regexp.MustCompile(tag)
anchoredTag = anchored(tag)
// anchoredTagRegexp matches valid tag names, anchored at the start and
// end of the matched string.
anchoredTagRegexp = regexp.MustCompile(anchoredTag)
anchoredTagRegexp = regexp.MustCompile(anchored(tag))
digestPat = `[A-Za-z][A-Za-z0-9]*(?:[-_+.][A-Za-z][A-Za-z0-9]*)*[:][[:xdigit:]]{32,}`
// DigestRegexp matches valid digests.
// DigestRegexp matches well-formed digests, including algorithm (e.g. "sha256:<encoded>").
DigestRegexp = regexp.MustCompile(digestPat)
anchoredDigest = anchored(digestPat)
// anchoredDigestRegexp matches valid digests, anchored at the start and
// end of the matched string.
anchoredDigestRegexp = regexp.MustCompile(anchoredDigest)
anchoredDigestRegexp = regexp.MustCompile(anchored(digestPat))
// nameComponent restricts registry path component names to start
// with at least one letter or number, with following parts able to be
// separated by one period, one or two underscore and multiple dashes.
nameComponent = expression(alphanumeric, optional(repeated(separator, alphanumeric)))
namePat = expression(optional(domain, literal(`/`)), nameComponent, optional(repeated(literal(`/`), nameComponent)))
namePat = expression(
optional(domain, literal(`/`)),
nameComponent,
optional(repeated(literal(`/`), nameComponent)))
// NameRegexp is the format for the name component of references. The
// regexp has capturing groups for the domain and name part omitting
// the separating forward slash from either.
NameRegexp = regexp.MustCompile(namePat)
anchoredName = anchored(
optional(capture(domain), literal(`/`)),
capture(nameComponent,
optional(repeated(literal(`/`), nameComponent))))
// anchoredNameRegexp is used to parse a name value, capturing the
// domain and trailing components.
anchoredNameRegexp = regexp.MustCompile(anchoredName)
anchoredNameRegexp = regexp.MustCompile(anchored(optional(capture(domain), literal(`/`)), capture(nameComponent, optional(repeated(literal(`/`), nameComponent)))))
referencePat = anchored(capture(namePat), optional(literal(":"), capture(tag)), optional(literal("@"), capture(digestPat)))
referencePat = anchored(capture(namePat),
optional(literal(":"), capture(tag)),
optional(literal("@"), capture(digestPat)))
// ReferenceRegexp is the full supported format of a reference. The regexp
// is anchored and has capturing groups for name, tag, and digest
// components.
ReferenceRegexp = regexp.MustCompile(referencePat)
identifier = `([a-f0-9]{64})`
// IdentifierRegexp is the format for string identifier used as a
// content addressable identifier using sha256. These identifiers
// are like digests without the algorithm, since sha256 is used.
IdentifierRegexp = regexp.MustCompile(identifier)
anchoredIdentifier = anchored(identifier)
// anchoredIdentifierRegexp is used to check or match an
// identifier value, anchored at start and end of string.
anchoredIdentifierRegexp = regexp.MustCompile(anchoredIdentifier)
anchoredIdentifierRegexp = regexp.MustCompile(anchored(identifier))
)
// literal compiles s into a literal regular expression, escaping any regexp